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SCANNER surveys for Local Roads User Guide and

1. Reliability Overall Maximum Code factor factor factor points Rut depth greater of LLRT 1 0 1 0 1 0 100 nearside and offside LRRT LPV higher scoring of LV3 0 8 1 0 0 8 80 or om ANd Iom LV10 0 6 0 6 60 Whole carriageway LTRC 1 0 0 6 0 6 60 cracking Nearside wheel track LLTX Varies 1 0 Varies 75 50 taxtu depth 0 75 to 0 3 0 75t00 3 or30 Maximum total points 315 to 270 Table 3 3 Relevance and reliability factors for revised SCANNER RCI used with 2007 08 3 3 4 surveys and subsequent years The values are then summed for each nominally 10m subsection of the survey giving a value a between zero no reported deterioration and 370 maximum score on all parameters for the original SCANNER RCI 28 3 3 5 3 3 6 3 3 7 3 3 8 3 4 3 4 1 Section 4 The SCANNER Road Condition Indicator b between zero no reported deterioration and 315 maximum score on all parameters for the revised SCANNER RCI The maximum value does not have any special significance it simply represents a sub section on which all the parameters exceed the upper threshold value There is no way to convert a score from the revised RCI to the original RCI or vice versa Either the original or the revised RCI may take a higher value Many lengths of road will have a score of zero and this will include carriageways in a wide range of conditions from nearly new and nearly perfect to quite worn and q
2. ee SCANNER edge roughness LEDR is obtained from analysis of the laser profile heights reported within consecutive transverse profiles along the road The method reports the roughness within a half metre wide strip adjacent to the road edge This SCANNER edge roughness measure LEDR can indicate where the road surface at the road edge is likely to be in poor condition but it cannot identify which particular surface defects are likely to be present The 15 SCANNER User Guide and Specification Volume 3 measure indicates irregularities in the edge surface but would not identify a regular surface containing surface deterioration in the form of cracking or crazing Figure 2 4 Figure 2 4 Illustration of the principle of LEDR measurement on a minor road Figure 2 5 Examples of edge steps LES1 and LES2 identified by SCANNER on a minor road 16 2 6 6 2 6 7 2 6 8 2 6 9 2 6 10 2 6 11 Section 3 SCANNER parameters SCANNER edge steps LES1 and LES2 assess the height of the stepping present within the transverse profile adjacent to the identified road edge Figure 2 5 a LSL1 LES1 Percentage of reporting length with small step down at the road edge 20 to 50mm b LSL2 LES2 Percentage of reporting length with large step down at the road edge greater than 50mm The SCANNER edge step measurement seems to provide a good indication of verge over riding on rural roads It can also
3. traffic calming features or to failures in local reinstatement 10m variance is influenced by both short and medium length undulations The medium length undulations possibly arising from localised subsidence of reinstatements and subsurface utilities and bay irregularities on concrete roads a Extremely high levels of 10m variance may indicate extensive pavement distress b Very high levels of 10m variance over long sections of the road network may indicate the need for extensive repairs including possibly reconstruction c Very high levels of 10m variance over short lengths may be related to traffic calming features or to local reinstatement failures and require localised reconstruction d High levels of 10m variance may be associated with road camber and profile changes at junctions 30m variance is influenced by short medium and longer length undulations It includes the longer wavelength features that may indicate subsidence or large scale foundation distress such as a road built on embankment over soft ground or through an area of mining subsidence It mainly affects vehicles travelling at high speeds over 50mph and particularly vehicles with a longer wheel base such as buses coaches and rigid bodied trucks travelling at high speed On most local roads the measured value of 30m variance is affected much more by road geometry than on trunk roads and motorways and does not seem to correlate with any specific maint
4. 2 7 8 2 7 9 2 7 10 2 7 11 2 7 12 20 Single Line Texture The texture of the surface helps to provide an indication of the high speed skidding resistance which may affect road safety It is in this context that the measured SMTD LLTX is applied Specifications and thresholds for achieving and maintaining texture depth have been set in the UK for many years on roads carrying large volumes of high speed traffic in order to maintain skid resistance performance in wet conditions In this context skid resistance refers to the skid resistance at HIGH SLIP SPEED i e where the tyre is skidding over the surface texture at speeds up to that of actual traffic speed In contrast skid resistance measurement by devices such as the SCRIM or GripTester is made at LOW SLIP SPEED typically less than 20km h because the test wheel is only slipping over the surface at a fraction of the vehicle speed during the test As a result there can be confusion over whether texture depth measurements such as SMTD or MPD can be used instead of low slip speed skid resistance measurements The SCANNER research established no evidence of any relationship between texture depth measured by laser SMTD and low slip speed skid resistance measured by SCRIM Hence texture depth cannot be used as a reliable indication of the low slip speed skid resistance measured by SCRIM or GripTester The skid resistance at low slip speeds is believed to be
5. The Stationery Office London Available online at http www ukroadsliaisongroup org pdfs p03 well maintained _highways paf Schupke P and Zohrabi M 2006 Using SCANNER data for Maintenance Management on Local Roads Part1 Final Report Mott MacDonald Southampton Available online at http Awww ukroadsliaisongroup org roads use_ data htm Schupke P and Zohrabi M 2006 Using SCANNER data for Maintenance Management on Local Roads Part2 Appendices Mott MacDonald Southampton Available online at http Awww ukroadsliaisongroup org roads use_data htm SCOTS 2007 Results of SRMCS surveys Society of Chief Officers of Transportation Scotland Available online at http www scotsnet org uk Smith S 2006 SCANNER HMDIF Specification UKPMS Document Number 71 UKPMS support office Chris Britton Consultancy Guildford Surrey Available online at http Awww ukpms com owner_forum shared_files 071v0107 pdf Tachtsi L and Taggart AJA 2004 Confirm TTS requirements and Base Data Atkins Highways Asset Management Group Birmingham Available online at http www ukroadsliaisongroup org roads confirmation htm Viner H Abbott P Dunford A Dhillon N Parsley L and Read C 2006 Surface texture measurement on local roads TRL Published Project Report PPR148 TRL Limited Wokingham Available online at http www ukroadsliaisongroup org roads surface_texture htm Watson PJ McRobbie SG and Wright MA 2004 Initial study of
6. and deceleration conditions Comparative research has shown that both methods are capable of meeting all the requirements of the SCANNER specification Benbow E Nesnas K and Wright MA 2006 The GM method is better suited for conditions where the vehicle can be operated with less stopping and starting and where the road winds or there are a lot of turns The HRM method is better suited for conditions where there is more frequent stopping and starting and less bends or turns Engineers consulted during the SCANNER research expressed concern about measuring ride quality As well as general ride quality which is measured through the longitudinal profile parameters engineers were concerned about isolated bumps which affect ride quality but do not show up clearly in the average LPV values As part of the SCANNER research Benbow E Nesnas K and Wright MA 2006 an entirely new measure has been developed to identify isolated bumps based on the central difference method CDM The bump intensity is reported in UKPMS as a single value either 0 indicating no significant bump within the sub section length or 1 indicating one or more significant bumps within the sub section The SCANNER Bump intensity is not used in either the SCANNER RCI or the UKPMS treatment rules Longitudinal profile variance is the main factor controlling ride quality and hence user perception of road condition service level experienced by the road user I
7. be used to provide an indication of the level of edge support and an implied indication of the condition of the verge Trials have shown that the transverse profile measurement does not always extend over the edge of carriageway and even when it does the edge detection method does not always detect the edge of carriageway because there is no particular feature in the transverse profile For example in an urban area there may be a kerb which is easily detected or a drive entrance flush with the road surface which is not detected In a rural location there may be a grassy verge with a definite step up or step down which is easily detected or an extent of bare ground level with the carriageway which is not detected Therefore it is very important to know the number of transverse profiles within which the edge of the carriageway has been detected This is reported as SCANNER edge coverage LEDC This value indicates the percentage of the reporting length where the profiles have been measured over the edge of the road Where the value is low less confidence should be placed in particular on the measure of edge stepping The SCANNER edge condition measurements are not used in the SCANNER RCI Neither are they used in UKPMS for treatment selection A single SCANNER edge deterioration indicator has been proposed that combines the results of edge deterioration measurements transverse variance edge roughness and edge step Figure 2 6 w
8. of St Teath The length between the two purple circles was identified as a potential scheme length Section 6 References g Q 1 e SNe 6rd yd K S z OZ ARS OE irestart ds a dige Dannonchape Ss Y SS eTbinnabroad Low o d a line owe oS RAN Trevorrian Map Mew Grid Reference 206055 84111 21906 12 34 i maene Pta F lt anteglos Ss Kay kle CAA ee of eH Tyn wg EEO ee igi gt v Ds We D SY SH BIS 2 Helsbury TRN Tredarrup k Trewethen 4 135 i Si 4 7 W 2 as s AS AT 1 i NZ Perera i Erreganet dis LA 3A X Hamatethyi J Ana 1 oe 4 afi sd at lev OER i SSS A LA BO SO OSS a AAN R Scale 1 25000 o oe Bed pon OS 1 SOD R er S Skm wh he pemilzsion of he conkoller or Her Meles vs Ststoneny ON Crown copmighi Urse No 100015880 Comwell County coundi 2005 Figure 4 1 Cornwall County Council and WDM Limited Map Mew D gt g Y Treroosel Farm 8am P R Scale 1 5686 ced upon OF 1 1000 Ras kr 1 K Bon View Trabellan 18 906 11 19 0 300m ict kim wiih Pe permission of he contailer or Her Maes s Sislorey ON Crown copmighi Ucense No IOOD1SS80 orwell County Council 205 Figure 4 2 courtesy of Cornwall County Council and WDM Limited SCANNER RCI data overlaid on a map of part of Cornwall pic
9. path Therefore the SCANNER specification has been extended to include measurements in both wheel paths At present only the measurement in the left nearside wheel path is used in the SCANNER RCI and in UKPMS indicative treatment selection The enhanced LPV has been introduced to replace moving average LPV Enhanced LPV correlated with users perceptions of ride quality better than moving average LPV and is a more stable and hence a more reliable parameter The moving average LPV measurements in the left nearside wheel path have been to enable comparison with the values measured using TTS in 2004 and SCANNER in 2005 and 2006 However once there is a reasonable overlap between the moving average and the enhanced LPV measurements the requirement to report moving average LPV may be dropped 11 SCANNER User Guide and Specification Volume 3 Figure 2 1 2 4 6 2 4 7 2 4 8 2 5 2 5 1 12 Example of a principal road where poor ride quality has been reported Research showed that although users perceptions of ride quality can be related to longitudinal profile variance the LPV was not always successful in identifying large local bumps arising from features such as large local depressions e g failed patches The bump intensity has been introduced to identify these features The measure simply reports the presence or not of severe bumps in each 10m length This measure is currently not used in the SCANNER RCI The re
10. representatives by TRL Limited by the Chris Britton Consultancy by SCANNER survey contractors by Halcrow by Nick Lamb Consultancy Ltd and by UKPMS developers This document was prepared by TRL Limited under the PCIS support contract SCANNER User Guide and Specification Volume 3 Contents 1 Introduction nineteen ii a a re ett atte Renee NEE aeaa 7 ti What iS SCANNER Z rn raer ae a a a a a aari 7 1 22 SG AINE RO SUIV CYS 2s 2cesr oh hehe ted ca cet ee on ech takava kondi at ene csere Ara shots 7 SCANNER Parameters ses ceccacisuzcttesteneegn ser edenacacanadavescocuctan sy eedesteacepeeutssauaeeeneiaveseeceaanrs 9 2al WMUPQQUCUONeiaiccsace ces scarce ate e cates capes ie capes cou teeta tec atau Seana A is cease ae 9 2 2 Location TEICTEMEING A oe eS oe eh 9 2 3 Road Geometry sirosis vad aise Dead ated ea OEE aaa dae eed 10 2 4 Longitudinal protile ccavct cinerea ekacea eee een lees 10 25 ransverse PIOMlesacc cee he ee ee 12 26 Edge Conditi nscieen ia cis tedden eae I es 14 20 MOXMUTG depth sim a ooeoe se Sageteene viel a cee ee eae aes 18 So E E Ke Pepe ere eR rr RES an are a ar ee eee PORTER rear Os ee re ee 22 The SCANNER Road Condition INGiCator eee cceeeeeeeeenceeeeeeeeesnaeeeeeeeeesnneeeeeeeeneneaaees 25 3 1 Requirements of a Road Condition Indicator cceeceeseeeeeeeeeeeeeeeeeeeeeeeeeaees 25 3 2 Developing the SCANNER RCI 0 eeeeeeccceceeeeessecceeeeeeseeeeeeeeeneeessneeeeeeeeseenaeees 2
11. specified in Volume 4 Further technical information on the measurement and use of the SCANNER parameters is also given in Annex 1 Location referencing All data delivered by the SCANNER survey is provided in reference to the Employer s road network The fitting of the data to the network is carried out by the Contractor Contractors often achieve this by manually recording the location of section change points during the survey e g with a manual event marker installed in the survey vehicle Following the completion of the survey the events recorded are aligned with the network information provided by the Employer so that the survey data can be delivered within an HMDIF file relative to distance travelled within section and lane By aligning SCANNER data with the UKPMS defined road network i e ensuring that the network provided to the Contractor is the same as that defined within the Employer s UKPMS it can be used with other survey data such as visual inspection data and with historic data that is referenced directly to the UKPMS network The data can also be used with any functionality specified through UKPMS such producing the SCANNER Road Condition Indicator In addition the position of the survey vehicle during a SCANNER survey is reported at intervals of approximately 10m along the survey route The three SCANNER position co ordinates are reported as UKPMS code LCOO SCANNER survey parameter OBVAL 30
12. standard rut depths are unexpectedly high SCANNER also reports transverse profile unevenness LTAD which is a measure of the Absolute Deviation of the First Derivative ADFD of the Transverse Profile This parameter assesses how much the slope of the transverse profile changes from point to point across the carriageway An even surface would have a low ADFD value whereas a saw tooth profile would have a high ADFD value SCANNER transverse profile unevenness LTAD does not contribute to either the SCANNER RCI or the UKPMS indicative treatment selection rules The measure may be of use when assessing a narrow road where the transverse profile is uneven but is not appearing as deep rutting Note that the research programme recommended that two transverse profile parameters required in earlier versions of the SCANNER specification should be discontinued However these are retained within UKPMS to enable all the data reported in 2005 and 2006 to be processed in future UKPMS code SCANNER survey parameter LLAD SCANNER absolute deviation of 1st derivative of nearside of transverse profile LRAD SCANNER absolute deviation of 1st derivative of offside of transverse profile Note that transverse profile measurements may be affected by factors such as traffic calming features The Contractor is required to identify the presence of these features and remove the transverse profile data that may be affected This will lead
13. that do not form part of a proposed scheme should be investigated to determine whether any local repairs are necessary to maintain minimum standards of safety or to arrest deterioration of road condition UKPMS also provides an approach to identifying treatments from SCANNER data More information is available on the UKPMS website UKPMS identifies three indicative treatments from SCANNER data These are a Strengthen based on rut depth 3m longitudinal profile variance whole carriageway and wheel track cracking intensity values b Resurface based on rut depth 3m longitudinal profile variance whole carriageway and wheel track cracking intensity values c Surface treatment based on texture depth and whole carriageway cracking values These indicative treatments are broadly consistent with the results from the SCANNER RCI but which also includes 10m longitudinal profile variance and gives slightly different emphasis to the relative importance the various parameters Over a wider area a number of schemes may be identified treatments selected and costs estimated using a pavement or asset management system These 39 SCANNER User Guide and Specification Volume 3 4 3 4 3 1 4 3 2 4 3 3 4 3 4 4 3 5 4 3 6 4 4 4 4 1 40 can be assembled into a planned maintenance programme to be delivered over a number of years Prioritising within available resources It is possible that the lengt
14. to gaps in the reported transverse profile parameters Edge Condition SCANNER measures the edge condition profile of the pavement The measurements of edge condition are actually derived from the measured transverse profile which are analysed to produce the derived SCANNER edge condition parameters These are reported at intervals of approximately 10m using UKPMS codes 2 6 2 2 6 3 2 6 4 2 6 5 Section 3 SCANNER parameters UKPMS code SCANNER survey parameter LTRV SCANNER transverse variance LEDR SCANNER edge roughness LES1 SCANNER road edge step L1 between 20 and 50mm step down LES2 SCANNER road edge step L2 greater than 50mm step down LEDC SCANNER edge coverage Figure 2 3 Illustration of the principle of the LTRV measurement on a minor road The SCANNER measurement of edge deterioration is based on the initial identification of the road edge within the transverse profile This is used to separate the verge from the road and enables the calculation of various parameters SCANNER transverse variance LTRV is the difference in the average variance of the transverse profile height in the left and right halves of the transverse profile after the edge of carriageway has been detected and any profile measurements to the left of the edge of carriageway have been suppressed It is a measure of the difference in the condition of the two halves of the carriageway Figure 2 3
15. 3 7 1 3 7 2 Section 4 The SCANNER Road Condition Indicator From 2007 2008 road condition in Scotland has similarly been reported on the basis of the RCI However unlike England the reported figure applies to the total public road network including unclassified roads and reports on the portion falling in both the red and amber bands Although not statutory performance indicators the RCI results for each road class are also available specifying separately the portions falling in the red and amber bands Prior to 2007_08 the Scottish results were reported on the basis of the SPI which did not include data on cracking In Scotland a single national survey contract has been awarded to collect the data from which the results are provided to individual local authorities for local maintenance management purposes and for reporting to Audit Scotland as part of their annual statutory PI returns Details of the Scottish results can be found on the SCOTS website www scotsnet org uk by following the link on the home page to Road Condition Surveys Benchmarking between local authorities The SCANNER research has investigated whether there is any evidence for grouping English local authorities for oenchmarking comparisons in the same way that Scottish local authorities seem to fall into a number of natural groups based on the percentages of their networks that are urban or rural On the basis of a detailed analysis of the resu
16. 4 6 5 5 50 Texture depth measurements single line Texture measurement devices work by measuring the distance between the sensor and the road surface As the sensor moves along the road changes in this distance are recorded at short intervals the sampling interval is typically 1mm due to the surface texture The measured texture profile of the surface is analysed by firstly removing filtering large features arising from the longitudinal profile and then generating a characteristic value from the filtered data Both the SMTD and MPD algorithms can be described in these terms The main difference between these two methods is in the way that the height of the texture is estimated the SMTD measurement is essentially a root mean square RMS measure of the texture both above and below the mean level whereas MPD measures the height of the highest peaks above the mean level The measures are correlated but the relationship between the two measures will depend on the shape of the surface texture and therefore on the type of surface This is illustrated in Figure 6 1 see Viner et al 2006 which compares two hypothetical surface shapes with the same SMTD value For one surface the MPD value is higher than the SMTD value and for the other surface the MPD value is lower than the SMTD value MPD value SMTD value same as below MPD value SMTD value same as above Illustration of SMTD and MPD on different surface prof
17. 5 3 3 How the SCANNER RCI value is calculated cc cceeeeeeeeeeeeeeeeeeeeeeeeeeeeneeaees 26 3 4 Reporting road condition using the SCANNER RCI cceeeceeeeeeeeeeeeeeeeeeneeees 29 3 0 National reporting iesin aa a ee Ge ee t 32 3 6 Benchmarking between local authoritieS cccccceeeeseeeeeeeeeeeeesseeeeeeeeeseeeeeees 33 3 7 Future development of the SCANNER RCL cccceceeeeeeeeeeeeeeeeeeeneeeeeeeeneneaees 33 Using SCANNER results 4 52 0et ce acetal Acs i eee Aas at cheeses cee utara er 34 4 1 Knowledge of asset condition ceeeeseecceeeeeeeeeeeceeeeeeteeceeeeeeneeesseeeeeeeeenennanees 34 4 2 Identifying Maintenance need cee eeeeeeeeeeeeeeeeeeeeeeeeeeaeeeeeeeeeeneeeeeeeeneneaaees 36 4 3 Prioritising within available resources ccceeeeeeeeeeeeeeeeeeneeeeeeeeeeenneeeeeeeennennaees 40 4 4 Area or region Condition repOrting eecceceeeeeseeeceeeeeeeeeeeeeeeeeeeesseeeeeeeeeseeneeees 40 Referente Senari e eben Rebels a baleen genie al aalen eka EAE E AE ade ate 41 Annex 1 SCANNER parameters 2 0 2 s054 fscieeeeecetee ees cnenee senate eevee dieeeednae need 43 Gals Road Gemet y eee cs is cede ae UR atid dees 43 6 2 Longitudinal PROTN SS tac case eres eaeeceesde ned nanana kaituh aaeeio pepadawavocee sesdsuacueeedvtscbucactes 44 6 3 Transverse profile and rut depth sss cc os hc yc cee cole ses o 46 OA Edge Condition se 2c 4 eave Mine ee ta ee ati se i 47 6 5 Textur
18. ANNER RCI on non principal classified B roads Section 6 References SCANNER RCI REVISED values for non principal classified C roads Parameter Lower Upper Importance Reliability Weighting Maximum threshold threshold score Average rut depth greater of LLRT LRRT LLRT 10mm 20mm 1 1 1 100 LRRT Ride quality higher scoring of LV3 and LV10 LV3 7mm 17mm 0 8 1 0 8 80 LV10 35mm 93mm 0 6 1 0 6 60 Whole carriageway cracking intensity LTRC LTRC 0 15 2 1 0 6 0 6 60 Average texture depth nearside wheel path LLTX Non built up 0 6mm 0 3mm 0 5 1 0 5 50 Built up 0 6mm 0 3mm 0 3 1 0 3 30 Maximum point score for each nominally 10m long sub section 290 or 270 Table 7 6 Revised parameter thresholds and weightings for SCANNER RCI on non principal classified C roads 59 SCANNER User Guide and Specification Volume 3 SCANNER RCI REVISED values for unclassified U roads Parameter Lower Upper Importance Reliability Weighting Maximum threshold threshold score Average rut depth greater of LLRT LRRT LLRT 10mm 20mm 1 1 1 100 LRRT Ride quality higher scoring of LV3 and LV10 LV3 8mm 20mm 0 8 1 0 8 80 LV10 41mm 110mm 0 6 1 0 6 60 Whole carriageway cracking intensity LTRC LTRC 0 15 2 1 0 6 0 6 60 Average texture depth nearside whee
19. CANNER only takes account of whether the crack lies mainly within the defined wheel track Both whole carriageway cracking and wheel track cracking contributed independently to the original SCANNER RCI used in 2006 and 2007 Currently only the whole carriageway cracking contributes to the revised SCANNER RCI 23 SCANNER User Guide and Specification Volume 3 2 8 7 2 8 8 2 8 9 2 8 10 2 8 11 2 8 12 2 8 13 24 Both whole carriageway cracking and wheel track cracking contribute independently to the UKPMS indicative treatment selection Whole carriageway cracking contributes to strengthen resurface and surface treatment Wheel track cracking only contributes to strengthen and resurface SCANNER identifies cracking by collecting video images and analysing them automatically The automatic detection and measurement of cracking on a road surface is technically very challenging Most road surfaces are essentially grey and images of the road surface have visual texture in terms of variability in the grey scale across the image The variation in the visual texture across the image tends to mask the cracks which are normally visible in the image as darker features B Figure 2 9 Longitudinal and transverse cracking on a minor road The identification of cracking relies on interpretation of the image recorded by the particular crack identification software The
20. MA 2004 TTS Initial Review Review of Survey Methods TRL Published Project Report PPR001 TRL Limited Wokingham Available online at http Awww ukroadsliaisongroup org roads review_survey htm McRobbie SM and Wright MA 2005 TTS research crack detection on local roads Phase 1 TRL Published Project Report PPRO74 TRL Limited Wokingham Available online at http Awww ukroadsliaisongroup org roads crack_detection htm McRobbie S 2006 SCANNER Condition Indicator Parameter Thresholds and Weightings TRL Unpublished Project Report UPR IE 130 06 TRL Limited Wokingham Also available as TRL Published Project Report PPR238 March 2007 TRL Limited Wokingham Available online at http www pcis org uk index php p 6 12 0 detail 0 675 McRobbie S Walter L Read C Viner H and Wright A 2007 Developing SCANNER Road Condition Indicator parameter thresholds and weightings TRL Published Project Report PPR199 TRL Limited Wokingham Available online at http www pcis org uk index ohp p 6 12 0 detail 0 674 Nesnas K McRobbie SG and Wright MA 2004 Initial study and development of transverse profile analysis TTS on local roads TRL Published Project Report PPR0O14 TRL Limited Wokingham Available online at htto www ukroadsliaisongroup org pdfs 04 11 30 20Final PPR014 TProfile 1 PDF Roads Liaison Group 2005 Well maintained Highways Code of Practice for Highway Maintenance Management Department for Transport
21. ROADS UK ROADS BOARD SCANNER surveys for Local Roads User Guide and Specification Volume 3 Advice to Local Authorities Using SCANNER survey results Version 1 0 2011 Edition SCANNER User Guide and Specification Volume 3 Contents Amendment Record This report has been issued and amended as follows Issue Revision Description Date Signed 1 0 1 0 First published version of March 2011 specification 2011 Department for Transport Great Minster House 76 Marsham Street London SW1P 4DR Telephone 44 0 207 944 8300 Website www dft gov uk Using SCANNER survey results Acknowledgement This SCANNER User Guide has been developed from the SCANNER specification used in 2009 It incorporates many detailed changes based on experience of using the SCANNER specification in 2005 06 2006 07 and 2009 the TTS specification before that in 2003 04 and 2004 05 and a wide range of comments from interested parties It includes the results of research on developing SCANNER commissioned on behalf of the UK Roads Board The previous SCANNER specifications were based on the original TRACS Type Surveys for the Principal Road Network Specification and Advice Note produced for the UK Roads Board by the Chris Britton Consultancy and TRL Limited Throughout the development of the TTS and SCANNER specifications considerable assistance and support has been given by members of the SCANNER Implementation Group including local authority
22. S One approach is to divide the 45 SCANNER User Guide and Specification Volume 3 6 2 15 6 3 6 3 1 6 3 2 6 3 3 6 3 4 46 measurements into a number of colour coded bands so that lengths of road with high values are readily apparent A first approach would be to use the thresholds defined in the SCANNER RCI for the individual parameters and colour code the lengths green amber and red This could be used to show where both 3m and 10m variance are high together and where the values in both wheel paths are high together as the basis for identifying lengths where ride quality is poor and targeting maintenance treatments designed to improve ride quality Alternatively other thresholds could be set either to give more condition bands or to adjust the percentage of the network falling within a band as a way of identifying the lengths in the worst condition Transverse profile and rut depth In addition to the familiar measurement of rutting SCANNER also provides a number of measures derived from the transverse profile The transverse unevenness ADFD is a totally new approach to defining the transverse shape of a pavement and there is little practical experience of how well it correlates with either user perception of the surface condition of a road the surface or structural condition or the need for maintenance However research has shown the new measure correlates well with measured rut depth and that it also detec
23. S radius of Curvature LFAL SCANNER or TTS Crossfall LGRD SCANNER or TTS Gradient SCANNER measures road geometry from the vehicle not on the road itself Therefore there may be differences between the values measured on the path the vehicle follows and those that a surveyor might measure carrying out a detailed total station survey There may be slight differences between the values on the road centreline and the centre of each lane and between the centrelines in each lane However research has shown that these differences are likely to be relatively small in most places on local roads It is recommended that Curvature the inverse of radius of curvature is used when presenting geometry information along the length of a road rather than radius of curvature Curvature is larger where the road bends and smaller where it is straight and is more easily interpreted by eye e g on a graph than radius of curvature Longitudinal profile SCANNER reports the longitudinal profile of the road in both the nearside and offside wheel paths as a number of parameters each reported at intervals of approximately 10m as UKPMS codes 2 4 2 2 4 3 2 4 4 2 4 5 Section 3 SCANNER parameters UKPMS code SCANNER survey parameter LV3 SCANNER or TTS 3m moving average LPV left nearside LLO3 SCANNER 3m enhanced LPV left nearside LV10 SCANNER or TTS 10m moving average LPV left nearsid
24. SCANNER or TTS x co ordinate OBVAL 31 SCANNER or TTS y co ordinate OBVAL 32 SCANNER or TTS z co ordinate The x and y co ordinates are OSGB36 National Grid Co ordinates eastings and northings and the z co ordinate is altitude height These co ordinates can be used to assist in accurately locating the data on the Employers road network Experience has shown that Contractors sometimes have difficulty aligning SCANNER survey data with road networks Problems occur where road networks have not been kept up to date where section start and end points have not been accurately defined or have not been clearly defined SCANNER User Guide and Specification Volume 3 2 2 7 2 3 2 3 1 2 3 2 2 3 3 2 4 2 4 1 10 To improve the fitting of SCANNER data the Employer is required to provide National Grid Co ordinates of the section start and end points to the Contractor This enables Contractors to align SCANNER survey data using the measured position co ordinates The requirements for identifying section start and end points are specified in Volume 4 section 2 2 with outline guidance on selecting section start and end points for SCANNER surveys Road Geometry SCANNER measures the gradient the cross fall and the radius of curvature which are reported at intervals of approximately 10m as UKPMS codes UKPMS code SCANNER survey parameter LCRV SCANNER or TT
25. aight edge and wedge Rutting is a symptom of deterioration in the wearing course or the foundation and is an indicator of the need for structural maintenance either a wearing course treatment or reconstruction Figure 2 2 Engineers and asset managers may use rut depth measurements from SCANNER exactly as they would use machine measured rut depth in UKPMS or as they would use rut depth measured by trained and experienced inspectors Average rut depth in the left or nearside and right or offside wheel paths contributes to UKPMS indicative treatment selection rules Rut depths are also used in the SCANNER RCI 2 5 3 SCANNER also reports a further measurement of rutting called Cleaned Rut Depths The SCANNER research programme identified that rutting can be affected by the presence of features at the edge of narrow roads such as 13 SCANNER User Guide and Specification Volume 3 2 5 4 2 5 5 2 5 6 2 6 2 6 1 14 verges that result in erroneously high rut depths The Cleaned Rut Depth represents the results of calculating the rutting following the application of an algorithm to identify the road edge hence removing edge features from the rut calculation The Cleaned Rut Depth is currently undergoing a trial phase to determine its stability and accuracy and is not included in the SCANNER RCI or treatment selection Users may wish to compare the Cleaned Rut Depth data with standard rut depths on narrow roads in particular when the
26. arameters used within the calculation of the original and extended RCI To obtain an RCI value each parameter is scored between two thresholds a lower threshold below which there is no need to consider maintenance and an upper threshold above which further deterioration does not increase the score These thresholds were based on engineers experience of each parameter The score increases linearly between the lower and upper threshold from zero at the lower threshold to 100 at the higher Figure 3 1 demonstrates this procedure for rutting The thresholds for each parameter are given in Annex 2 The score for each parameter is then multiplied by two factors each having a value between zero and one One factor reflects the relevance or importance of the measurement to the maintenance condition of the road The other reflects the reliability of the method of measurement a The values used in the original SCANNER RCI for surveys carried out in 2005 06 and 2006 07 and reported in 2006 and 2007 are given in Table 3 2 b The values to be used in the revised SCANNER RCI for surveys carried out in 2007 08 and subsequent years and reported in 2008 and subsequent years are given in Table 3 3 Section 4 The SCANNER Road Condition Indicator UKPMS code SCANNER survey parameter Original Revised RCI RCI Ride quality 3m longitudinal profile variance in nearside v v LV3 left wheel path Ride
27. ated road carriageway condition surveys The specification defines the set of data that should be collected by survey vehicles on local roads and how this should this processed and delivered The specification also defines the required level of accuracy for the data and how survey vehicles machines will be tested to ensure that they are compliant with the specification acceptance testing in order to obtain an accreditation certificate The specification includes the requirement for annual re testing for continuing compliance with the specification to secure further annual accreditation certificates The parameters delivered by the SCANNER survey are intended for use within a pavement management system to report the condition of the road and to guide and aid road carriageway maintenance management decisions as part of an overall asset management system SCANNER surveys SCANNER surveys have been developed to provide a consistent method of measuring the carriageway surface condition of classified local roads throughout the United Kingdom They have been developed to support five different requirements Figure 1 1 a As the basis for developing a detailed knowledge of the current condition and value of the paved carriageway asset b Replacing CVI and DVI surveys as the basis for defining the optimum treatment selection on classified roads and the optimum timing of treatment to prioritise treatment and minimise the whole life c
28. be because there is more traffic on these parts of the network d The overall picture confirms the importance of maintaining good levels of texture depth particularly on rural roads and particularly where the skid resistance is also low The average texture depth SMTD in the left or nearside wheel paths LLTX is used both within the SCANNER RCI and also contributes to UKPMS indicative treatment selection rules 2 7 13 2 7 14 2 7 15 2 7 16 2 7 17 2 7 18 Section 3 SCANNER parameters Multiple Line Texture Simple single line texture depth on its own is often a poor indicator of the surface condition or the need for maintenance treatment of a road carriageway surface because it can be acceptable at low medium or high values a Where high friction surfacing is used low texture depth is good If the average texture depth increases this may indicate wear which is not good b Where a modern negatively textured surface is used medium texture depth is good Low texture depth is not good and may indicate excess bitumen on the surface due to poor mix design or subsequent fatting up High texture depth is not good indicating wear and fretting c Where HRA and surface dressings are used high texture depth is generally good although very high texture depth may indicate fretting or chip loss and low texture depth is not good indicating wear embedment of chippings or fatting up The SCANNER research sho
29. cator Requirements of a Road Condition Indicator There are a number of differing requirements for a road carriageway condition indicator a To identify lengths of road where the condition has deteriorated and the level of service may also have deteriorated As an input to planning detailed investigation and maintenance b To summarise the condition of a section or length within a network As an input to maintenance planning c To rank the lengths of road where the condition has deteriorated and maintenance treatment may be required As an input to allocating resources between different lengths of road requiring treatment d To identify the type or types of treatment required on a length of road As an input to estimating the overall requirement for resources e To summarise the overall condition of a road network so that some value can be ascribed to the network As an input to asset valuation and management f To summarise the overall condition of a road network so that comparisons can be drawn between different areas As an input to performance indicators 9 To summarise the overall condition of a road network so that trends in condition can be observed from year to year As an input to national or local monitoring The SCANNER Road Condition Indicator RCI has been developed as a way of characterising the condition of the road carriageway which fulfils some but not all of the requirements It identif
30. d where the amber threshold has been set at 40 30 Section 4 The SCANNER Road Condition Indicator Original SCANNER RCI with amber at 20 points m Red G Amber E Green A Q c 2 Q o 2 a Road category Figure 3 3 Percentage length of red amber and green from a representative sample of local roads using the original SCANNER RCI 78 91 Original SCANNER RCI with amber at 40 points 60 14 m Red Amber E Green Proportion B Road category C Figure 3 4 Percentage length of red amber and green from a representative sample of local roads with original SCANNER RCI and amber green threshold at 40 points Revised SCANNER RCI with amber at 40 points 68 36 66 33 Red Am ber Green Proportion Road category Figure 3 5 Percentage length of red amber and green from a representative sample of local roads with revised SCANNER RCI and amber green threshold at 40 points 3 4 4 Note that because of the accuracy of the network referencing the precise start and end position of each 10m sub section length will change from year to year Therefore care must be taken when aligning subsections and comparing results 31 SCANNER User Guide and Specification Volume 3 3 5 3 5 1 3 5 2 3 5 3 3 5 4 3 5 5 3 5 6 3 5 7 32
31. d SCANNER cracking parameters which are reported as average values within the HMDIF at intervals of approximately 10m using UKPMS codes UKPMS code SCANNER survey parameter LTRC SCANNER or TTS Cracking whole carriageway LWCL SCANNER or TTS Left Wheel Track Cracking Intensity LWCR SCANNER or TTS Right Wheel Track Cracking Intensity LRCR SCANNER Transverse reflection cracking LSUR SCANNER Surface Deterioration Parameter The SCANNER measurement of cracking typically covers a survey width of 3 2m although this can vary with the survey vehicle minimum is 2 9m Whole carriageway cracking is obtained by overlaying the crack map with a grid covering the whole survey width and summing up the areas of the grid squares containing cracks The method by which the whole carriageway cracking intensity is obtained from the crack map is given in volume 5 An example of a cracked road surface is shown in Figure 2 9 Wheel track cracking intensity is reported over two tracks each of width 0 8m centred on the wheel paths Consequently the area considered for wheel track cracking is typically about 50 of the area considered for whole of carriageway cracking SCANNER wheel track cracking is very different from classic visually recognised wheel track cracking This is because the engineer or inspector takes account of the orientation of the crack along the wheel path before recognising and reporting it Whereas S
32. dding resistance or the stiffness of the pavement layers a Surface skidding resistance can be measured using systems like SCRIM or Griptester Research carried out as part of SCANNER development has shown that surface texture CANNOT be used as a 35 SCANNER User Guide and Specification Volume 3 4 1 11 4 1 12 4 1 13 4 2 4 2 1 4 2 2 4 2 3 4 2 4 4 2 5 36 proxy for skidding resistance on local roads in the UK Viner et al 2006 b The stiffness of the pavement layers can be measured using systems such as Deflectograph or Falling Weight Deflectometer FWD and interpreted as a measure of pavement strength and residual life in the case of the Deflectograoh SCANNER measurements CANNOT at present be interpreted to give a measure of residual life Measurements of skidding resistance and pavement deflection stiffness can be combined with SCANNER measurements in pavement and asset management systems Other measurements such as ground penetrating radar and the results from coring and test pits can also be combined with SCANNER results in some asset management systems The reports from visual inspections can also be combined with SCANNER measurements in UKPMS and used in pavement and asset management systems Identifying maintenance need The results from the SCANNER survey can be expressed as the SCANNER Road Condition Indicator RCI This is a measure of the overall condition of each nominall
33. e LL10 SCANNER 10m enhanced LPV left nearside LLBI SCANNER Bump intensity CDM left nearside LRO3 SCANNER 3m enhanced LPV right offside LR10 SCANNER 10m enhanced LPV right offside LRBI SCANNER Bump intensity CDM right offside The longitudinal profile is the shape of the road in the direction of travel Figure 2 1 Longitudinal profile variance LPV is a measure of how much the road undulates This can be reported at any scale from a small scale where it is a measure of bumpiness to a large scale where it is a measure of the topography LPV is important for two reasons it is the main factor controlling ride quality and hence user perception of road condition and it can be a good indicator of defects in the surface course the binder course and the base road base The SCANNER research programme recommended a number of changes to the SCANNER specification that were introduced from 2007 onwards In summary a the measurement of longitudinal profile is required in both wheel paths b a new method of analysing the data was added to give the enhanced LPV as well as the moving average LPV c a new measurement of oump intensity was introduced d 30m LPV is no longer reported Research showed that users perceptions of ride quality on local roads are significantly affected by the longitudinal profile in the right offside wheel path as well as the left nearside wheel
34. e depth measurements Single line eee eeeeeteeeeeeeeeeeneeeeeeeeeeeeenaees 50 6 6 Texture depth measurements multiple line eee eeeeeeee eee eeeeeeeeeeeeeneeeeaees 51 ANNEX 2 SCANNER RO aranera a a a a O a 54 Using SCANNER survey results Foreword This document is one of a series of five describing the requirements for SCANNER Surveys Surface Condition Assessment of the National Network of Roads It replaces the revised SCANNER specification first published in March 2006 and subsequent updates of February 2007 and 2009 The five Volumes are 1 Introduction to SCANNER surveys 2 Advice to Local Authorities Procuring Surveys 3 Advice to Local Authorities Using SCANNER Survey Results 4 Technical requirements SCANNER Survey Data and Quality Assurance 5 Technical requirements SCANNER Survey Parameters and Accreditation This Volume 3 Using SCANNER survey results explains the background to SCANNER Surveys and gives further guidance on the interpretation of processed SCANNER data It contains advice on receiving and using SCANNER data interpreting the results for local asset management and maintenance and producing and understanding performance indicators Volume 1 provides a brief introduction to the requirements for SCANNER surveys and is intended to be read as a free standing document as well as providing an overview of the other four volumes It includes a glossary of terms and a l
35. e the possibility of comparing the SCANNER EDI with the SCANNER RCI on a map basis to identify places where the need for general carriageway maintenance and edge treatment coincide and places where only edge treatment may be required The simplest approach to using the SCANNER edge condition parameters for UKPMS indicative treatment selection would be to use the SCANNER ECI over 100m lengths as a direct substitute for the UKPMS edge condition indicator based on CVI surveys and to select values of the SCANNER edge deterioration indicator over 100m reporting lengths to match the UKPMS Edge Cl thresholds UKPMS description UKPMS Edge Condition Indicator UKPMS Indicative treatment Negligible edge deterioration 0 points no treatment required Local edge deterioration 2 0 points and lt 40 points edge patch Partial edge deterioration 2 40 points and lt 70 points edge reconstruct partial depth General edge deterioration 2 70 points edge reconstruct full depth Matching SCANNER EDI to UKPMS CVI edge deterioration Alternatively it would be possible to develop a more detailed approach using the individual SCANNER edge condition parameters or the value of the SCANNER edge deterioration indicator over 10m reporting lengths to build up an indicative treatment selection 49 SCANNER User Guide and Specification Volume 3 6 5 6 5 1 6 5 2 6 5 3 Figure 6 1 6 5
36. eatment of a road carriageway surface because it can be acceptable at low medium or high values a Where high friction surfacing is used low texture depth is good If the average texture depth increases this may indicate wear which is bad b Where a modern negatively textured surface is used medium texture depth is good Low texture depth is bad and may indicate excess bitumen on the surface due to poor mix design or subsequent fatting up High texture depth is bad indicating wear and fretting c Where HRA and surface dressings are used high texture depth is generally good although very high texture depth may indicate fretting or chip loss and low texture depth is bad indicating wear embedment of chippings or fatting up Therefore average texture depth is an unsatisfactory parameter for measuring surface condition because without knowing the surface type it is impossible to determine what range of texture depths is desirable what range is acceptable and what range is undesirable The SCANNER research Viner et al 2006 has shown that it is possible to measure the variability of texture depth along and across road surfaces and that this can be associated with road surface wear although it is also associated with 51 SCANNER User Guide and Specification Volume 3 6 6 4 6 6 5 6 6 6 6 6 7 52 the presence of other features such as road markings The SCANNER survey therefore requires
37. ection in accordance with the highway authority s policies should be the basis for ensuring that the road remains in a safe and serviceable condition At present UKPMS does not provide condition projection for the SCANNER RCI or SCANNER parameters Area or region condition reporting SCANNER provides a numerical RCI score for each subsection of the road network There are at least two ways that these scores may be combined to characterise the condition of a length of road or a network over an area a One is simply to average the score over the length This gives a single value which may be useful for considering the average condition and ranking the relative condition of lengths or areas This is most useful when comparing schemes on a worst first basis b An alternative is to count the number of lengths in a condition worse than a pre determined standard This is the approach taken in England for national reporting where the red length i e total length of the network with gt 100 points has been adopted to report the overall condition of principal roads as BV223 NI168 and other classified roads as BV224a NI169 Section 6 References 5 References Audit Commission 2007 Performance Indicators Best Value Data Available online at http www audit commission gov uk performance dataprovision asp Benbow E Nesnas K and Wright MA 2006 Shape surface form of Local Roads TRL Published Pro
38. edge deterioration TTS on local roads TRL Published Project Report PPRO15 TRL Limited Wokingham Available online at http www ukroadsliaisongroup org roads edge_deterioration htm Watson P Wright A and McRobbie S 2006 Edge deterioration on Local Roads TRL Published Project Report PPR084 TRL Limited Wokingham Available online at http Awww ukroadsliaisongroup org roads edge_condition htm 42 6 1 6 1 1 Section 6 References Annex 1 SCANNER parameters Road Geometry Road geometry is INVENTORY not CONDITION information It does not change much from year to year and does not generally indicate the need for maintenance The absolute values of road geometry i e the values measured by a total station survey are unlikely to change from year to year except where major work is carried out on the road leading to a change in alignment or surface profile Therefore any slight changes in SCANNER measured road geometry from year to year are more likely to be due to variations in the driving line and the relative positions of the sub section lengths over which the averages are reported rather than physical changes on the road However changes from year to year may be used to detect physical changes in the network for example a new roundabout at a junction giving access to a new development or inaccuracies in aligning the SCANNER survey data with the existing network These changes would have to be isolated from changes ar
39. enance requirements Therefore it is of little practical relevance on the majority of local classified and unclassified roads High levels of profile unevenness do not only affect ride quality High levels of profile unevenness particularly in the 3 m and 10 m wavelength ranges have been shown to contribute to increased dynamic loading of the pavement hence accelerating the structural deterioration Extremes of profile unevenness can also lead to increased stopping distances and can have an adverse effect on vehicle manoeuvrability Both 3m and 10m LPV in the left nearside wheel path contribute to the SCANNER RCI In the original SCANNER RCI used until 2007 they contributed independently i e the scores are added together However there is an overlap between lengths with high 3m variance and lengths with high 10m variance partly because the shorter wavelength features that are measured by 3m variance also contribute to 10m variance so they are not wholly independent measures Therefore they are treated as related measures with only the higher scoring of the two contributing to the overall score in the revised SCANNER RCI used from 2008 onwards Only the 3m LPV in the left nearside wheel path contributes to UKPMS indicative treatment selection rules Values of 3m and 10m LPV and the SCANNER bump intensity can be displayed on road network maps using pavement and asset management systems that include a GIS or are linked to a GI
40. f specific lengths of road a The video survey information provides a qualitative record of the condition of the road at the time of survey and complements the quantitative data gathered by SCANNER Together they can provide most of the information an engineer or asset manager needs to have a detailed record of the carriageway asset condition at a particular time as well as qualitative information about the appearance of the street including footways verges and street furniture b Increasingly local authorities are building detailed inventories of their road assets SCANNER provides quantitative information about the condition of the carriageway and a simultaneous video record can be a useful way of checking for the presence location and appearance of the asset inventory items at a particular time Typically the video survey data consists of a sequence of good quality digital images along the survey often taken at 5m intervals These can be strung together to produce a virtual video of progress or viewed individually for more detailed examination These will require greater capacity in the data storage system and development of the pavement or asset management system to enable the SCANNER results to be compared with the photographic images ina GIS presentation This can be a large data storage and management exercise particularly if a video survey is carried out with every SCANNER survey SCANNER does NOT measure surface ski
41. file of the road in the direction of vehicle travel along the road the longitudinal profile This is important for two reasons it is the main factor controlling ride quality and hence user perception of road condition and it can be a good indicator of defects in the surface course the binder course and the base roadbase b The profile of the road across the direction of travel the transverse profile This includes measuring rut depth This is important for two reasons ruts or other transverse unevenness features can affect steering or cause water to pond both of which may affect road safety and it can be a good indicator of defects in the surface course the binder course and the base roadbase c The texture of the surface This can be important for two reasons It helps to provide high speed skidding resistance on fast roads which may affect road safety Variations in texture depth along or across the road can indicate surface wear and the presence of defects in the surface course d Cracking visible at the surface This can be important for two reasons It may indicate deterioration of the surface course or of deeper seated defects in the binder course and base It may allow water to penetrate through the pavement layers and weaken the foundations SCANNER measures the survey parameters more or less continuously along the road The survey contractor processes the measurements either on the survey vehicle during the
42. from year to year In order to make comparisons between years it is more appropriate to combine the results along routes sections or networks National reporting Until 2009 the SCANNER RCI was used to report at the national level the condition of principal BV223 and other classified BV224a road networks These indicators report the length as a of an authority s network that falls within the red band In 2009 BV223 and BV224a were replaced by NI168 and NI169 respectively More information about the English requirements is available on the Department for Transport website Department for Transport 2007 The original SCANNER RCI was used as the basis for reporting the English BV223 and Bv224a up to 2007 based on the most recent survey results i e from 2005 06 and 2006 07 for reporting in 2007 The revised RCI was used for reporting BVPI NI from 2008 again based on the most recent survey results i e from 2006 07 and 2007 08 for reporting in 2008 The results in England are reported by the Audit Commission Note that during 2005 06 there were problems with the automatic software used to detect cracking in the images collected by one of the machines used in England This made the reported amounts of both whole carriageway and wheel track cracking unreliable Therefore the SCANNER RCI was not a reliable method of for comparison between those authorities that used that survey machine compared with other local authorities a
43. g the variation in texture depth along the road between left and right wheel paths LLTV versus LRTV d Comparing the variation in texture depth along the road between the centre line and the wheel paths LCTV versus LLTV and LRTV Or alternatively LCTV versus the higher of LLTV and LRTV e The overall variation in texture depth across the road LTVV f Extreme values of texture depth LTO5 and LT95 For a comparing the average texture depth between left and right wheel paths Comparing LLTM and LRTM A road surface in good condition would be expected to have similar values Therefore dissimilar values are likely to indicate a road surface that is not in a good condition unless the SCANNER wheel paths are on dissimilar materials for example where patching or reinstatement has taken place A similar approach would be taken when considering b c and d A road in good condition would be expected to have a relatively low variation in texture depth unless the sub section included lengths of dissimilar materials Therefore a high variation in texture depth LTVV is likely to indicate a road surface that is not in good condition The absolute value of variance is likely to vary with the average texture depth being lower on a low textured surface in good condition such as high friction surface and somewhat higher on a coarse textured surface such as HRA or surface dressing As the centreline value is the value least likely t
44. h of road categorised as requiring planned maintenance soon may exceed the annual budget available The SCANNER RCI provides one way of prioritising maintenance schemes on a worst first basis The average value of the SCANNER RCI can be calculated over the length of each of the proposed schemes This enables the schemes to be ranked in the order of their SCANNER RCI scores In the St Teath scheme example shown above the average RCI score was 104 based on the original SCANNER RCI However there is nothing special about an average SCANNER RCI score The same average value could be obtained from a combination of very high scoring lengths with lower scoring lengths or by a consistent run of medium high scoring lengths Equally there is nothing special about adopting a worst first approach The engineer or asset manager should consider the SCANNER RCI value together with all the other information available about the current condition and likely future changes in condition of the carriageway and the local authority s current and expected future service requirements for the road before deciding on the most cost effective treatment and the optimum timing for the treatment of the road A high SCANNER RCI score does not of itself indicate that the road is in an unserviceable or unsafe condition A high SCANNER RCI score only indicates that the carriageway subsection is likely to need planned maintenance soon Regular safety insp
45. hich is based on the same type of approach as the SCANNER RCI A single indicator for edge deterioration would reduce the work required in managing the multiple edge parameters delivered by the SCANNER survey It would offer a degree of continuity with the edge condition indicator offered by current CVI surveys and would be more appropriate for the network level assessment The single edge deterioration indicator can be calculated in UKPMS using the SCANNER Edge Cl weighting set 17 SCANNER User Guide and Specification Volume 3 ICONDITIONINOICATOR Edge steps ea e oo o Edge roughness Figure 2 6 Illustration of the components of the edge condition indicator 2 6 12 Note that because the edge deterioration parameters are derived from the transverse profile measurements may be affected by factors such as traffic calming features The Contractor is required to identify the presence of these features and remove the transverse profile data that may be affected This will lead to gaps in the reported transverse profile and edge parameters 2 7 Texture depth 2 7 1 SCANNER measures the texture of the pavement The surface texture depth measured by SCANNER is the coarser element of macro texture and the finer element of mega texture of the pavement surface 2 7 2 SCANNER texture can be separated into two groups single line and multiple line texture 2 7 3 The measurements are analysed to produce the SCANNER text
46. holds and weightings for the SCANNER RCI should be retained for the immediate future at least until local authorities are more familiar with the interpretation of SCANNER survey results 33 SCANNER User Guide and Specification Volume 3 4 4 1 4 1 1 34 Using SCANNER results Knowledge of asset condition At the simplest level the engineer or asset manager responsible for managing a road network needs to know a Which roads they are responsible for b What condition they are in c What maintenance is required and d The best time to carry it out The SCANNER accredited survey vehicle measures carriageway condition from the perspective of a moving vehicle It surveys one lane of the carriageway at a time and produces numbers a quantitative measure of carriageway condition SCANNER produces vastly more data than visual surveys and therefore requires a much greater capacity in the pavement asset management and data storage systems both software and hardware To be able to use SCANNER survey data effectively the engineer or asset manager will need comprehensive IT support both commercial software programmes such as pavement management systems and asset management systems linked to geographic information systems GIS and the hardware to support them in terms of display screens personal computers servers network capacity bandwidth and data storage systems SCANNER makes four sorts of measurement a The pro
47. ies lengths where the condition is poor and enables their condition to be summarised and ranked It can also be used to summarise the overall condition of part or all of a road network so that comparisons may be made between different areas and trends in condition can be observed from year to year It has specifically NOT been developed as a method of identifying the TYPES OF TREATMENT required on a length of road or to ascribe a VALUE toa network Developing the SCANNER RCI The SCANNER RCI has been developed through a process of research development testing and refinement This was carried out in three stages a Preliminary research leading to the TTS Defects Index Preliminary Analysis Cartwright and Pickett 2004 b A review of the proposals and recommendations by the Defects Index Working Group set up by the UK Roads Board in 2005 supported by tests of the RCI on principal roads McRobbie 2006 This led to the 25 SCANNER User Guide and Specification Volume 3 3 3 3 3 1 3 3 2 3 3 3 26 original values used in the SCANNER RCI in 2006 on 2005 06 survey data c Review of the results with the initial values by the SCANNER RCI Working Group set up by the UK Roads Board in 2006 supported by further tests on classified roads McRobbie et al 2007 This led to recommendations for a revised set of values used for reporting in 2007 and 2008 How the SCANNER RCI value is calculated Table 3 1 shows the p
48. ighting Maximum threshold threshold score Average rut depth greater of LLRT LRRT LLRT 10mm 20mm 1 1 1 100 LRRT Ride quality higher scoring of LV3 and LV10 LV3 4mm 10mm 0 8 1 0 8 80 LV10 21mm 56mm 0 6 1 0 6 60 Whole carriageway cracking intensity LTRC LTRC 0 15 2 1 0 6 0 6 60 Average texture depth nearside wheel path LLTX Non built up 0 7mm 0 4mm 0 75 1 0 75 75 Built up 0 6mm 0 3mm 0 5 1 0 5 50 Maximum point score for each nominally 10m long sub section 315 or 290 Table 7 4 Revised parameter thresholds sa weightings for SCANNER RCI on principal A roads 57 SCANNER User Guide and Specification Volume 3 SCANNER RCI REVISED values for non principal classified B roads Parameter Lower Upper Importance Reliability Weighting Maximum threshold threshold score Average rut depth greater of LLRT LRRT LLRT 10mm 20mm 1 1 1 100 LRRT Ride quality higher scoring of LV3 and LV10 LV3 5mm 13mm 0 8 1 0 8 80 LV10 27mm 71mm 0 6 1 0 6 60 Whole carriageway cracking intensity LTRC LTRC 0 15 2 1 0 6 0 6 60 Average texture depth nearside wheel path LLTX Non built up 0 6mm 0 3mm 0 75 1 0 75 75 Built up 0 6mm 0 3mm 0 5 1 0 5 50 Maximum point score for each nominally 10m long sub section 315 or 290 Table 7 5 58 Revised parameter thresholds and weightings for SC
49. iles In the UK the texture depth is typically obtained as the Sensor Measured Texture Depth SMTD The Mean Profile Depth is the standard method for specifying texture depth in Europe It is the basis of the texture measurement that is needed to implement the European Friction Index as a harmonised scale of friction measurement and is likely to form the basis for texture measurement within European Performance Indicators for road pavements The SCANNER research investigated the relationship between SMTD and MPD measured on typical local roads in England Viner et al 2006 Figure 6 2 shows the results of grouping the SMTD values into bands with a width of 0 1mm SMTD and plotting the average MPD values for each band with the error bars encompassing 95 of the values in the band It is apparent that the relationship between SMTD and MPD is only approximately linear at higher 6 5 6 Figure 6 2 6 6 6 6 1 6 6 2 6 6 3 Section 6 References texture depths increases in SMTD produce smaller increases in MPD and the overall trend flattens off The trend can be represented by the equation MPD 1 42 x SMTD This is also plotted as the solid line in Figure 6 2 1 5 mean SMTD mm Relationship between SMTD and MPD measured on a sample of local roads Texture depth measurements multiple line Average texture depth on its own is a poor indicator of the surface condition or the need for maintenance tr
50. ising from the variability in the SCANNER equipment The extent to which small changes in values are to be expected from year to year and hence the thresholds for detecting gross changes have not been formally quantified and may vary depending on road geometry However the SCANNER accuracy requirements for geometry would lead us to expect that measurement differences from year to year should not exceed 1 5 absolute In general the road geometry has either been designed to the standards then prevailing or improved to the standards then prevailing to meet the changing requirements of traffic over the past 100 years In most cases road geometry is more or less acceptable for the current use of the road Places where it is wholly unacceptable will have been identified by experience in service Places where the requirement for the road changes significantly e g due to development will be identified and improved as part of traffic and network management Therefore when using SCANNER road geometry data the engineer is looking for places where the road geometry is somewhat unacceptable for some reason Or where the geometry is Unusual and affects the quality of service including safety One particular example would be the use of SCANNER data to identify some of the site categories for implementing a skidding resistance policy However road geometry is not easily altered by maintenance Improvement requires realignment or reconstructio
51. ist of the SCANNER parameters as annexes Volume 2 contains advice to Local Authorities about procuring SCANNER surveys under the SCANNER Specification and is to be read in conjunction with the other documents It includes advice on preparing contact documents inviting bids assessing tenders and managing contracts It includes a model contact document as an annex Volume 3 Using SCANNER data explains the background to SCANNER Surveys and gives further guidance on the interpretation of processed SCANNER data It contains advice on receiving and using SCANNER data interpreting the results for local asset management and maintenance producing and understanding performance indicators and reporting NRMCS results Volume 5 Technical requirements for SCANNER Survey Parameters and Accreditation defines the technical requirements for the parameters provided by the machine developer including acceptance and consistency testing and accreditation It describes the requirements for accreditation of the Equipment It also describes the requirements for consistency testing and for the reporting and delivery of data from SCANNER accredited surveys SCANNER User Guide and Specification Volume 3 Typical survey vehicles e a Yotta DCL ARAN1 vehicle 1 2 1 2 1 Section 1 Introduction Introduction What is SCANNER SCANNER stands for Surface Condition Assessment for the National Network of Roads and is a specification for autom
52. ject Report PPR131 TRL Limited Wokingham Available online at http Awww ukroadsliaisongroup org roads road_surface htm Cartwright RA and Pickett A 2004 TTS Defects Index Preliminary Analysis Final Report version 2 Chris Britton Consultancy Guildford Available online at http Awww ukroadsliaisongroup org roads tts_defects htm Cartwright R le Doujet K and Spong C 2005 Consistency of TTS results on Local Roads Interim Report Chris Britton Consultancy Guildford Available online at http Awww ukroadsliaisongroup org roads consistency data htm Cartwright R and Spong C 2006 Consistency of TTS results on Local Roads Final Report Chris Britton Consultancy Guildford Available online at http www ukroadsliaisongroup org roads consistency data htm Cartwright R 2007 TTS treatment rules A summary of TTS treatment rules in UKPMS UKPMS support office Chris Britton Consultancy Guildford Available online at http Awww ukpms com owner forum shared _files 112v0102 pdf County Surveyors Society 2004 Framework for Highway Asset Management CSS support officer Wiltshire County Council Trowbridge Wiltshire Available online at http Awww ukroadsliaisongroup org liaison asset_management htm Department for Transport 2006 Full Guidance on Local Transport Plans second edition Department for Transport London Available at http webarchive nationalarchives gov uk http www dft gov uk pgr regional Itp g
53. l path LLTX Non built up 0 6mm 0 3mm 0 5 1 0 5 50 Built up 0 6mm 0 3mm 0 3 1 0 3 30 Maximum point score for each nominally 10m long sub section 290 or 270 Table 7 7 Revised parameter RER A od for SCANNER RCI on unclassified roads 60
54. lts from 2005 06 surveys the work McRobbie et al 2007 has concluded a There are possibly three main groups of English highway authorities for comparing principal road networks but the groups overlap considerably b There are no obvious groups of English highway authorities for comparing other classified road networks English local authorities are much more diverse in their make up than Scottish local authorities and there are fewer obvious groupings for benchmarking purposes Therefore English local authorities would probably do better to select a limited number of other authorities to compare their performance in managing road networks based on a wider range of environmental social and economic factors rather than a limited number of characteristics of their road networks Future development of the SCANNER RCI The SCANNER RCI Working Group used the experience of using the SCANNER RCI on 2005 06 survey data in the development of the revised RCI The Working Group subsequently recommended that an extended SCANNER RCI should be introduced in the future perhaps as early as 2009 via a new weighting set that would include the new e g edge bump parameters However the Road Performance Management Group recommended postponement of the introduction of an extended RCI whilst the revised RCI was fully implemented and accepted by authorities The UK Roads Board therefore decided that the revised set of parameters thres
55. mm Rural C 15mm Linear 25mm Longitudinal LV10 B 21mm Linear 56mm profile 10m variance Urban C 45mm Linear 90mm Rural C 45mm Linear 130mm72 Whole LTRC B amp C 0 15 Linear 2 0 carriageway cracking intensity Wheel track LWCL B amp C 0 5 Linear 5 0 cracking LWCR intensity Nearside LLTX B amp C 0 6mm Linear 0 3mm wheel track texture depth SCORE 0 points 100 points Table 7 2 Thresholds and weightings for other classified roads in England in 2005 06 and 2006 07 BV224a 55 SCANNER User Guide and Specification Volume 3 Relevance and Reliability factors for SCANNER RCI 2005 06 and 2006 07 Family UKPMS Importance Reliability Overall Maximum Defect Code relevance factor combined points factor factor Rut depth LLRT 0 9 1 0 0 9 90 greater of LRRT nearside and offside Longitudinal LV3 0 8 1 0 0 8 80 profile 3m variance Longitudinal LV10 0 6 1 0 0 6 60 profile 10m variance Whole LTRC 0 9 0 55 0 5 50 carriageway cracking Wheel track LWCL 0 9 0 44 0 4 40 cracking LWCR intensity greater of nearside and offside Nearside LLTX 0 5 1 0 0 5 50 wheel track texture depth Maximum total points 370 Table 7 3 56 Relevance and Reliability factors for SCANNER RCI 2005 06 and 2006 07 Section 6 References SCANNER RCI REVISED values for principal A roads Parameter Lower Upper Importance Reliability We
56. n If SCANNER data is analysed to show places where the road geometry does not provide an acceptable level of service low cost traffic management signs and or speed restrictions may be as cost effective on minor local roads as realignment or reconstruction The SCANNER research identified several potential uses for road geometry information However many of these uses are associated with combining the geometry data with other datasets within a user s PMS One of the main barriers to using it effectively is therefore relative lack of accuracy of position location information in the other relevant data sets This makes it difficult to match the geometry data with the information in the other data sets 43 SCANNER User Guide and Specification Volume 3 6 2 6 2 1 6 2 2 6 2 3 6 2 4 6 2 5 6 2 6 6 2 7 6 2 8 44 Longitudinal profile There are at least two different methods of measuring the longitudinal profile one based on using accelerometers sometimes referred to as the GM method and the other using a reference beam sometimes referred to as the HRM or TRL method The GM method requires forward motion and testing to establish the minimum survey speed and maximum acceleration and deceleration at which it is reliable In principle the HRM method is capable of being operated at any speed including under stop start conditions Therefore the SCANNER acceptance testing requires the vehicles to be tested under acceleration
57. n maintenance requirement and may also affect ride quality and safety service level experienced by the road user The condition of the edge of the road which can be an indicator of the need for an edge treatment maintenance requirement and may also affect serviceability and safety The texture depth which may be required for serviceability and safety and the texture depth variability which may be an indicator of surface deterioration The presence and extent of surface cracking which can be an indicator of surface or structural deterioration and the need for maintenance SCANNER surveys are not visual inspections They do not identify the condition of a road in the same terms as a visual inspection In a visual survey a trained and experienced inspector interprets the visible signs in the overall context and reports the condition of a length of road carriageway In SCANNER surveys a machine measures parameters which have to be interpreted to produce a meaningful result 2 2 1 2 1 1 2 2 2 2 1 2 2 2 2 2 3 2 2 4 2 2 5 2 2 6 Section 3 SCANNER parameters SCANNER Parameters Introduction This section describes the SCANNER measurements the parameters derived from those measurements and the parameters delivered to UKPMS in an HMDIF file for subsequent processing The descriptions presented in this section are presented as guidance for users The formal technical requirements for the delivered data are
58. nd year on year There was no way of adjusting these results to make reliable comparisons Therefore the Audit Commission did not make any comparison between the results in terms of quartiles Neither were the results used as part of the Comprehensive Performance Assessment CPA scores The following discuss a few of the observations made during the research and review of the nationally reported indicators a There is evidence to suggest that there is a relationship between the percentage of built up principal roads in an authority i e roads with a speed restriction of 40mph or less and BV223 This may be associated with two factors Principal roads in towns a have more numerous junctions and b have more excavation and reinstatement by utility companies The junctions affect the longitudinal profile measurements ride quality and the reinstatements can affect both ride quality and crack detection giving rise to some apparent cracking where there is none b There is little evidence of a relationship between the percentage red length and the percentage of built up roads on other classified roads c The work undertaken on the development of the revised RCI led to quite significant changes in the thresholds and lesser changes in the weightings that are likely to markedly change the red and amber lengths in many local authorities and hence lead to significantly different BV224a 3 5 8 3 5 9 3 6 3 6 1 3 6 2 3 7
59. ning junctions with vehicles trying to squeeze past on the left with one wheel overrunning the verge c The size of vehicles may have increased so that wheel loading is closer to the carriageway edge for example larger farm tractors or LGV using a road only suitable for smaller vehicles There are two main aspects to the problem a Deterioration of the pavement edge due to excessive vehicle loading near the edge combined with inadequate foundations inadequate lateral support or water penetration b Deterioration of the verge caused by vehicle overrun leading eventually to dangerous conditions such as potholes forming adjacent to the carriageway In urban areas there can also be problems at the joint between kerb and surface course exacerbated by local failure of the drainage system This can be difficult to measure and identify where the edge of carriageway is hidden by parked cars or where the problems relate to local gradients and crossfall and ineffective surface drainage with local ponding and water penetration of the base and foundations The SCANNER research has delivered several parameters for the measurement of edge deterioration and has proposed the use of a single SCANNER edge deterioration indicator combining the transverse variance edge roughness and edge step based on the same type of approach as the SCANNER RCI Watson P Wright A and McRobbie S 2006 Hence each parameter is given a score based on its
60. o have been affected by traffic wear and therefore closest to the value when the surface was laid it could be used to normalise the texture variability Currently there is insufficient information to propose rules for the application of extreme values of texture depth LLO5 and LL95 53 SCANNER User Guide and Specification Volume 3 7 Annex 2 SCANNER RCI Definitions Thresholds and weightings for principal roads in England in 2005 06 and 2006 07 BV223 Family UKPMS Lower Weighting Upper Defect Code threshold threshold Rut depth LLRT 10mm Linear 20mm LRRT Longitudinal profile LV3 4mm Linear 10mm 3m variance Longitudinal profile LV10 21mm Linear 56mm 10m variance Whole carriageway LTRC 0 15 Linear 2 0 cracking intensity Wheel track cracking LWCL 0 5 Linear 5 intensity LWCR Nearside wheel track LLTX 0 6mm Linear 0 3mm texture depth SCORE 0 points 100 points Table 7 1 Thresholds and weightings for principal roads in England in 2005 06 and 2006 07 BV223 54 Section 6 References Provisional thresholds and weightings other classified roads in England in 2005 06 and 2006 07 BV224a Family UKPMS Class Lower Weighting Upper Defect Code threshold threshold Rut depth LLRT B amp C 12mm Linear 25mm LRRT Longitudinal LV3 B 4mm Linear 10mm profile 3m variance Urban C 7mm Linear 17
61. ore will gradually increase to a maximum value at which point it will increase no further Consequently certain values of SCANNER RCI will be more common than others These are sub sections where one or more parameters have reached a maximum score and the other parameters are not yet contributing 29 SCANNER User Guide and Specification Volume 3 3 4 2 This effect can be seen in Figure 3 2 which shows data from a representative sample of 16 local authorities in England and Scotland B C U Percentage of dataset 300 325 350 Figure 3 2 Distribution of original SCANNER RCI values from a representative sample of local roads 3 4 3 The research programme has carried out extensive investigation into the behaviour of the RCI using data from sample authorities A few of the observations made in that work are presented here to provide a context in which to place locally obtained RCI values a Figure 3 3 shows the percentage of lengths classified as Red Amber and Green within a sample of 16 authorities for the original RCI and where the amber threshold has been set at 20 b Figure 3 4 shows the percentage of lengths classified as Red Amber and Green within a sample of 16 authorities for the original RCI and where the amber threshold has been set at 40 c Figure 3 5 shows the percentage of lengths classified as Red Amber and Green within a sample of 16 authorities for the revised RCI an
62. ost of maintenance at a scheme or project level c Replacing CVI and DVI surveys as the basis for indicative treatment selection and budget estimation to enable local authorities to plan carriageway maintenance at a network level d As an indication of the overall condition of a defined road network to replace network level Deflectograph and CVI surveys SCANNER User Guide and Specification Volume 3 1 2 2 1 2 3 e Increasing level of detail As an indication of the overall condition of a specific length of road carriageway or of an area of a road network to establish long term A National reporting NRMCS SRMCS Zz Area Regional reporting LA Pl o N Prioritising within available resources Identifying maintenance need Knowledge of asset condition trends in road maintenance condition replacing CHART in NRMCS Figure 1 1 Use of condition data after Ekins and Hawker 2003 SCANNER surveys collect a number of different measurements and process them to produce a number of parameters that describe the condition of the road surface These include a e The longitudinal profile along the road which characterises the ride quality of the carriageway the service level experienced by the road user and can be an indicator of structural condition the maintenance requirement The transverse profile across the road including the presence of ruts which can be an indicator of structural conditio
63. quality 10m longitudinal profile variance in nearside v y LV10 left wheel path Rut depth Average rut depth measured in the nearside v v LLRD left wheel path Rut depth Average rut depth measured in the offside vy v LRRD right wheel path Cracking Whole carriageway cracking intensity v y LTRC Cracking Wheel track cracking intensity measured in the vy x LWCL nearside left wheel path Cracking Wheel track cracking intensity measured in the vy x LWCR offside right wheel path Texture depth Average SMTD measured in the nearside left y 4 LLTX wheel track Table 3 1 SCANNER parameters used in calculating the SCANNER RCI Figure 3 1 Rut depth Example of scoring a SCANNER parameter average rut depth 27 SCANNER User Guide and Specification Volume 3 Family UKPMS Importance Reliability Overall Maximum Code factor factor factor points Rut depth greater of LLRT 0 9 1 0 0 9 90 nearside and offside LRRT 3m LPV LV3 0 8 1 0 0 8 80 10m LPV LV10 0 6 1 0 0 6 60 Whole carriageway LTRC 0 9 0 55 0 5 50 cracking Wheel track cracking LWCL 0 9 0 44 0 4 40 intensity greater of nearside and offside piece Nearside wheel track LLTX 0 5 1 0 0 5 50 texture depth Maximum total points 370 Table 3 2 Relevance and reliability factors for original SCANNER RCI used with 2005 06 and 2006 07 surveys Family UKPMS Importance
64. quirement to report 30m moving average LPV is no longer part of the SCANNER specification Research showed that it did not correlate with user perception of road condition and that it can be affected by road geometry 30m LPV is not used either in the SCANNER RCI or in treatment selection in UKPMS Note that longitudinal profile measurements may be affected by factors such as traffic calming features and vehicle speed and acceleration The Contractor is required to identify the presence of these features and remove the longitudinal profile data that may be affected This will lead to gaps in the reported LPV parameters Transverse profile SCANNER measures the transverse profile of the pavement The measurements of the transverse profile are analysed to produce the derived SCANNER parameters which are reported as average values at intervals of approximately 10m using UKPMS codes Section 3 SCANNER parameters UKPMS code SCANNER survey parameter LLRT SCANNER or TTS left wheel path rut depth LLRD SCANNER nearside rut depth from cleaned profile LRRT SCANNER or TTS right wheel path rut depth LRRD SCANNER offside rut depth from cleaned profile LTAD SCANNER absolute deviation of 1st derivative of transverse profile PUGES c 19 Figure 2 2 Example of a principal road where ruts are beginning to form 2 5 2 Rut depth determined from SCANNER surveys corresponds to a measurement made with a 2m str
65. related to fine scale surface micro texture and the relative simplicity of a non contact laser measurement of texture depth would make it an attractive alternative to conventional skid resistance measurements if it were possible to measure texture depth at a sufficiently fine scale The SCANNER research found that even at the highest resolution texture lasers cannot at present produce a good representation of micro texture levels However research into the relationship between texture depth skid resistance and accident risk has shown that texture depth is a significant variable in explaining accident risk Research has found that a There are circumstances where low texture depths can be associated with greater incidence of accidents This trend appears to hold consistently for accidents on dry roads but it is not known whether this is because braking performance on dry roads is also better with higher surface texture or because the distinction between wet and dry is not reported accurately b For most site categories no correlation was observed between texture depth and the accident density accidents per km or accident rate accidents per 100 million vehicle km However this may reflect the small length of the network with low texture depths c The trends in accident density were not generally supported by a corresponding trend in accident rate suggesting that while more accidents occur on low textured surfaces this could
66. reliable and consistent measurement of the actual rut depth i e the rut depth that an inspector would measure with a 2m straight edge and wedge The rut depths from the cleaned transverse profile LLRD and LRRD have been introduced to replace the standard SCANNER or TTS rut depths LLRT and LRRT In principle there should be no difference between them except that the rut depths from the cleaned profiles should be a more accurate and reliable measurement At present the standard method is retained so that the results from the two methods may be compared over a wider set of data across the full range of local roads Preliminary experience indicates that the cleaned rut depth may be substituted directly for the standard rut depth values in 6 4 6 4 1 6 4 2 6 4 3 6 4 4 6 4 5 Section 6 References subsequent calculations The standard rut depth is used in the initial SCANNER RCI and will be used in the revised SCANNER RCI The cleaned rut depth may be used in an extended SCANNER RCI Edge condition There is one principal cause of edge deterioration the carriageway is too narrow for the traffic currently using the road This may be for a number of reasons For example a The volume of traffic may have increased since the road was built so that a single traffic lane is unable to cope with frequent two way traffic without encroaching on the edge of pavement or overrunning the verge b Queues forming at right tur
67. resolution of crack detection systems employed on current SCANNER survey equipment typically limits the minimum crack width detected to around 2mm The automatic systems quantify the extent of cracking in a different way from a visual inspection Consequently SCANNER cracking intensity does not replicate visual survey cracking data but will generally report a much lower percentage area of cracking than would be reported from a visual inspection The SCANNER research developed further algorithms for the reporting of crack parameters from the SCANNER crack map including transverse cracking and surface deterioration The method of identifying transverse reflection cracking is described in Volume 5 SCANNER transverse reflection cracking LRCR has been developed as a way of differentiating surface cracking by their cause as a guide to treatment selection Appropriate treatment options are likely to depend on construction type The method of identifying surface deterioration is also described in Volume 5 The SCANNER surface deterioration parameter LSUR has been developed as a way of detecting isolated areas containing crack like defects as opposed to continuous cracks Both of these new parameters are undergoing a trial period to assess their value and are not used in the SCANNER RCI or in treatment selection 3 1 3 1 1 3 1 2 3 1 3 3 2 3 2 1 Section 4 The SCANNER Road Condition Indicator The SCANNER Road Condition Indi
68. survey or in their offices after the survey post 4 1 10 Section 6 References processing fits the survey data to the road network and reports the results as characteristic values every few metres along the road Most of the parameters are reported as average values over survey subsection lengths which are approximately 10m long along the road They are reported using a UKPMS HMDIF file Smith 2006 which can be loaded into any UKPMS accredited pavement management system The reported survey parameters are described in more detail in section 3 SCANNER does not measure the condition of footways cycle paths or verges nor does it measure the appearance of the street from the perspective of a local resident a Quantitative information on the condition of footways cycle paths and verges could be gathered by visual inspections and combined with information from SCANNER surveys in a pavement management system b Qualitative information about the appearance of the street could be gathered through visual inspections or photographic surveys and combined with information from SCANNER surveys in an asset management system Although not part of the SCANNER core requirements SCANNER survey contractors will often offer video surveys as an extra dataset in conjunction with their SCANNER surveys This video data can be very useful both as a way of checking SCANNER survey coverage and of carrying out more detailed investigation o
69. t can be an indicator of defects in the surface course the binder course and the base roadbase and of the structural condition Most roads have been constructed to have an adequate ride quality so deterioration in ride quality can also be an indicator of pavement deterioration and distress SCANNER measures longitudinal profile variance LPV The short medium and long wavelength features found to have the most effect on vehicle ride are represented by 3m 10m and 30m LPV respectively The ride quality of the road surface is also affected by the size length and speed of vehicles In practice the shorter wavelengths tend to affect all vehicles whereas the longer wavelengths tend to affect longer and faster moving vehicles The relevance of LPV data will be affected by traffic calming measures such as speed humps cushions and gateway treatments High levels of 3m variance typically arise from short wavelength features such as faulting potholes and poor reinstatements including patches that cross the wheel path a Extremely high levels of 3m variance may also be linked with the presence of severe wheel path cracking or rutting 6 2 9 6 2 10 6 2 11 6 2 12 6 2 13 6 2 14 Section 6 References b Very high levels of 3m variance over long sections of the road network may indicate the need for extensive repairs including possibly reconstruction c Very high levels of 3m variance over short lengths may be related to
70. the measurement of texture in multiple measurement lines for use in assessing the variability The minimum requirement is to measure texture profile on at least three lines including the nearside and offside wheel paths and the line midway between them However Contractors can provide measurements in up to 40 lines The texture data reported as RMST in each measurement line is averaged for the regions covering the wheel paths and the centreline and reported in the SCANNER HMDIF These values can be used to assess the variability of the texture and hence identify deterioration The differences between the average values in the wheel paths and midway between them can be a useful diagnostic tool a For example where all three average values are consistently low this may indicative a surface designed with a low texture such as a high friction surface HFS b Where the average value midway between the wheel paths is consistently slightly lower than the values in the wheel paths this may indicate a negatively textured surface such as a porous asphalt or SMA Initially the values would be similar but traffic may keep the negative texture more open in the wheel paths than between them where dust and debris may reduce apparent texture depth measurements c Where the average value midway between the wheel paths is consistently higher than the values in the wheel paths this may indicate wear such as fatting up or chipping embedment in
71. the wheel tracks d Where the average values in the two wheel paths are significantly different from each other this may indicate wear either fatting up and embedment or the onset of fretting e Wherever there is variability in texture depth this is likely to indicate wear and surface deterioration The variability of texture depth along and across the pavement can be a useful indicator of surface condition Viner et al 2006 Explained very simply a newly laid surface tends to have a consistent average texture depth with low variability Over time the variability may increase due to a number of factors Particularly due to the effects of a traffic wearing away the surface b the environment over time ageing drying and stiffening the binders leading to localised loss of chippings and c local reinstatement or maintenance treatments creating a patchwork of areas with differing average texture depth values Different approaches may be taken to analysing the SCANNER data on surface texture variability These need to be tested against data from a representative range of local road surface types a Comparing average texture depth between left and right wheel paths LLTM versus LRTM 6 6 8 6 6 9 6 6 10 Section 6 References b Comparing average texture depth between the centre line and the wheel paths LCTM versus LLTM and LRTM Or alternatively LCTM versus average of LLTM and LRTM c Comparin
72. ts misshapen pavements where the ruts are not well defined Therefore the measure will sometimes be higher than the measured rut depths and sometimes lower With experience and once realistic thresholds have been determined for the different types and classes of local road this will become a practical indicator of deterioration in the surface shape At present there is no specific guidance on how transverse profile unevenness may be used but one simple approach would be to apply thresholds to the data to identify those lengths with the highest values and compare the results with the measurements of rut depth on a map basis Perhaps choosing the 85 threshold to set an amber level and the 97 5 threshold to set a red level Lengths where the unevenness is high and the rut depth is low are likely to require inspection to determine whether maintenance is required and if so what treatment to apply and when The SCANNER research developed a technique for identifying the edge of carriageway in a transverse profile that extends over the edge of the carriageway Nesnas K McRobbie SG and Wright MA 2004 This method enables the removal of features at the edge of carriageway from the transverse profile that may sometimes contribute to incorrectly high measurement of rut depth particularly in the left nearside wheel path Thus it is possible to calculate a rut depth from the cleaned transverse profile that is a more
73. ture courtesy of Detail of SCANNER RCI values overlaid on B3267 St Teath Cornwall picture 37 SCANNER User Guide and Specification Volume 3 4 2 6 Three photographs shown in Figure 4 3 Figure 4 4 and Figure 4 5 extracted from the forward facing video illustrate the general condition of the section Figure 4 3 Forward facing video image B3267 in St Teath Cornwall picture courtesy of Cornwall County Council and WDM Limited Figure 4 4 Forward facing video image B3267 near St Teath Cornwall picture courtesy of Cornwall County Council and WDM Limited 38 Figure 4 5 4 2 7 4 2 8 4 2 9 4 2 10 4 2 11 Section 6 References Selil cr Forward facing video image B3267 near St Teath Cornwall picture courtesy of Cornwall County Council and WDM Limited Using the more detailed information from the SCANNER survey contained within the pavement management system and the forward facing video structural patching and thin surfacing was the recommended treatment for this scheme It is apparent from this example that the maintenance scheme on this section will treat red amber and green subsection lengths with red and amber lengths predominating However as can be seen in Figure 4 2 the section to the west of St Teath contains isolated red and amber subsections within predominantly green section lengths Here it might not be practical to devise a planned maintenance scheme Isolated red and amber sections
74. tween the EDI and the manual reference was obtained with reporting lengths of 1km indicating that the measure was good for network level assessment of rural local roads but less efficient at identifying particular 10m lengths containing deterioration However a practical and realistic network level reporting tool would be to use average values over 100m reporting lengths 6 4 9 The research suggested that the following thresholds be applied to the 48 SCANNER EDI to classify lengths 6 4 10 6 4 11 6 4 12 Table 6 4 6 4 13 Section 6 References Green lt 10 points indicating 100m lengths likely to be in generally good condition Amber 2 10 points and indicating 100m lengths with some defects lt 30 points likely to need further investigation soon and Red 2 30 points indicating 100m lengths with more extensive defects likely to need planned maintenance soon Table 6 3 SCANNER Edge Deterioration Indicator overall scores Neither the SCANNER Edge Deterioration Indicator nor any of the individual edge condition parameters is used in the initial SCANNER RCI or in UKPMS indicative treatment selection rules The simplest approach to using the current SCANNER edge deterioration indicator for scheme development would be to display the averaged values over 100m lengths on a road network map to identify the places where red and amber lengths cluster for more detailed investigation This would also giv
75. uidance fit p fullquidanceonlocaltransport3657 paqe 5 Department for Transport 2007 Preliminary Guidance for BV223 and BV224a surveys in 2007 08 Department for Transport London Available online at http www dft gov uk pgr roads network local servicelevels Department for Transport 2007 Further Guidance for Surveys for BV223 and BV224a in 2007 08 Department for Transport London Available online at http www dft gov uk pgr roads network local servicelevels Ekins JDK and Hawker LG 2003 TRACS Type Surveys for local roads Scoping Study Final Report UK Roads Board London Available at http Awww ukroadsliaisongroup org pdfs p04 tts scoping study final report pdf Furness G Barnes S and Wright MA 2007 Crack detection on Local Roads Phase 2 TRL Published Project Report PPR147 TRL Limited Wokingham Available online at http Awww ukroadsliaisongroup org roads crack_detection htm Hooper R and Goodier A 2006a Department for Transport SCANNER research Geometry of Local Roads Scott Wilson Pavement Engineering Nottingham Available online at http www ukroadsliaisongroup org roads road_geometry htm Hooper R and Goodier A 2006b Department for Transport SCANNER research Other Visible Defects Scott Wilson Pavement Engineering Nottingham Available online at http Awww ukroadsliaisongroup org roads visible_defects htm 41 SCANNER User Guide and Specification Volume 3 McRobbie SG and Wright
76. uite old The resulting values can be divided into three bands representing the overall condition of the sub section Band Condition Threshold Threshold Original Revised RCI RCI RED Lengths in poor overall condition which are condition likely to require planned maintenance plan soon i e within a year or so on a worst P first basis There may be justification for maintenance postponing major repairs and only gt 100 gt 100 soon carrying out minor repairs to keep the road safe and serviceable in order to minimise whole life costs i e economic prioritisation AMBER Lengths where some deterioration is condition apparent which should be investigated to determine the optimum time for planned plan maintenance treatment There may be investigation e ae aches EREK gt 20 gt 40 justification for carrying out a lesser soon maintenance treatment sooner rather than more extensive treatment later in order to minimise whole life costs GREEN Lengths where the carriageway is zi N A N A condition generally in a good state of repair Table 3 4 Definitions of red amber and green carriageway condition Reporting road condition using the SCANNER RCI As the road condition deteriorates and as the SCANNER measured parameters change the score on a subsection length will start to increase depending on which parameters are changing As each parameter increases the individual sc
77. ure parameters These are reported at intervals of approximately 10m along the survey route using UKPMS codes 18 2 7 4 Section 3 SCANNER parameters UKPMS code SCANNER survey parameter Single Line Texture LLTX SCANNER or TTS Left Wheel Path Average Texture depth SMTD LLTD SCANNER Left Wheel Path Average Texture depth MPD UKPMS code SCANNER survey parameter Multiple Line Texture LLTM SCANNER Left Wheel Path Mean RMST Texture depth LLTV SCANNER Left Wheel Path RMST Variance LCTM SCANNER Centre Mean RMST Texture depth LCTV SCANNER Centre RMST Variance LRTM SCANNER Right Wheel Path Mean RMST Texture depth LRTV SCANNER Right Wheel Path RMST Variance LTO5 SCANNER Overall Texture Variability RMST 5th Percentile Value LT95 SCANNER Overall Texture Variability RMST 95th Percentile Value LTVV SCANNER Overall Texture Variability RMST Variance Two texture profile parameters that were required in earlier versions of the SCANNER specification are no longer required These are retained within UKPMS to enable all the data reported in 2005 and 2006 to be processed in future UKPMS code SCANNER survey parameter LCTX SCANNER or TTS Wheel Path Centre Average Texture depth SMTD LRTX SCANNER or TTS Right Wheel Path Average Texture depth SMTD 19 SCANNER User Guide and Specification Volume 3 2 7 5 2 7 6 2 7 1
78. ure depth across the road surface ROT bs Figure 2 8 Variations in texture depth along and across the road surface 2 7 19 Current laser texture measurement devices work by measuring the distance between the sensor and the road surface The laser technology used may be affected by the presence of a shiny reflective film of water over the surface Therefore texture depth measurements can be unreliable on wet roads 2 8 Cracking 2 8 1 SCANNER measures cracking on the surface of the pavement which is reported as the location of each crack identified in the form of a crack map Each crack has UKPMS code LMAP with parameters 22 2 8 2 2 8 3 2 8 4 2 8 5 2 8 6 Section 3 SCANNER parameters UKPMS code LMAP SCANNER survey parameter OBVAL 2 Crack length OBVAL 23 Offset position OBVAL 24 Angle OBVAL 25 Type code crack or joint The crack map is reported in the SCANNER HMDIF but UKPMS is not currently configured to use this information In future it may become possible to overlay the crack map on the visual image of the road surface and to overlay the crack map on a detailed map of the road in a UKPMS accredited system At present it is only possible to view the crack map using proprietary software provided by the survey companies This proprietary software differs between companies and has not been standardised as a SCANNER requirement The cracks are analysed to produce the derive
79. value and a weighting and the scores are combined to deliver the overall edge indicator value The research proposed the values in Table 6 1 for the lower and upper thresholds Values below the threshold score 0 values above the threshold score 1 47 SCANNER User Guide and Specification Volume 3 6 4 6 SCANNER parameter UKPMS code Tower Tupper Edge roughness LEDR 0 035 0 161 Transverse variance LTRV 7 24 71 1 Small edge step LES1 0 5 00 Large edge step LES2 0 0 Note that for LES2 both thresholds are zero This means that any non zero value for the parameter LES2 is normalised to 1 Table 6 1 Recommended thresholds for SCANNER edge parameters The value of the SCANNER edge deterioration indicator EDI is calculated as SCANNER EDI W X ScoreLepr Wy X ScoreLtrv WeiX Score_esi Wee x ScoreLesz 6 4 7 The weightings identified in the research are given in Table 6 2 Parameter UKPMS code Symbol Value Edge roughness LEDR Wr 30 Transverse variance LTRV Wtv 15 Small edge step LES1 WE1 25 Large edge step LES2 WE2 30 SCANNER EDI maximum EDI 100 value Table 6 2 Parameter weightings for SCANNER Edge Deterioration Indicator 6 4 8 The SCANNER Edge Deterioration Indicator can be calculated over greater reporting lengths by averaging the values reported for each 10m length over the required reporting length The research found that better agreement be
80. wed that measurement of the variability of texture depth along and across road surfaces can be associated with road surface wear Figure 2 7 although it is also associated with the presence of other features such as road markings The SCANNER survey therefore requires the measurement of texture in multiple measurement lines for use in assessing the variability The minimum requirement is to measure texture profile on at least three lines including the nearside and offside wheel paths and the line midway between them Figure 2 8 However Contractors can provide measurements in up to 40 lines The texture data reported as RMST in each measurement line is averaged for the regions covering the wheel paths and the centreline and reported in the SCANNER HMDIF These values can be used to assess the variability of the texture and hence identify deterioration The variability of the RMST texture values are discussed further in Section 6 6 Neither SCANNER average texture depths RMST in the left or nearside right or offside wheel paths and on the centre line nor texture depth variability and variance measurements contribute to the SCANNER RCI or the UKPMS indicative treatment selection rules Initial values for the thresholds and weightings for SCANNER average texture depths RMST and texture depth variance and variability have yet to be developed 2i SCANNER User Guide and Specification Volume 3 Figure 2 7 Variation in average text
81. y 10m subsection The combination of parameters in the SCANNER RCI is specified for local authority and national reporting purposes but has been designed to reflect the maintenance priority for the local authority engineer or asset manager The SCANNER RCI is described in greater detail in section 3 where it is noted that the SCANNER RCI scores each subsection using rules that depend on the road classification and speed restriction This can then be divided into three categories a GREEN lengths where the carriageway is generally in a good state of repair b AMBER lengths where some deterioration is apparent which should be investigated to determine the optimum time for planned maintenance treatment c RED lengths in poor overall condition which are likely to require planned maintenance soon i e within a year or so on a worst first basis When the SCANNER RCI values are plotted on a map of the road network they appear as a patchwork of red amber and green lengths An example is shown in Figure 4 1 and Figure 4 2 Figure 4 1 shows the SCANNER RCI marked on three roads the B3314 the B3266 and the B 3267 either side of the A39 in Cornwall It can be seen that the red amber and green subsection lengths tend to cluster together giving a visual impression of the overall condition of road lengths Figure 4 2 shows a detail of a short section of the B3267 between the A39 junction at Knightsmill and through the village

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