Excess emissions planning tool (EXEMPT) user guide - UK-Air
Contents
1. 1257 gasoline engineswith cy AA oa oa 000 1 61 gasoline engines with catalyst 185 243 Y 0 008 eam ana LC eI ogee ren 12 01 gasoline engines with catalyst 222122222 ee IE I II E E RI E 3 4 3 Graphs menu Clicking on lt GRAPHS MENU gt accesses another menu screen to choose which pollutant to plot the histogram of total excess emission integrated over all stages and for every vehicle within a given type as a function of vehicle for the conditions under study An example of one such plot for CO excess emission is given in Figure 7 for the data listed above Clicking on the lt RETURN gt on the graph takes the user back to the GRAPHS MENU AEA Technology Page 7 AEAT ENV R 0639 Issue 1 Figure 6 Graphs menu screen Excess emissions planning tool Graphs M enu CARBON DIOXIDE CHART CARBON MONOXIDE HYDROCARBON CHART PARTICULATES CHART NITROGEN OXIDES CHART AEA TECHNOLOGY THE INNOVATION BUSINESS Figure 7 Graph of CO excess emission T otal excess carbon dioxide emissions by vehicle type AEA TECHNOLOGY THE INNOVATION BUSINESS 1 60E 02 1 40E 02 1 20E 02 B 1 00 02 5 E 8 00E 01 E 6 00E 01 4 00E 01 2 00E 01 0 00E 00 Diesel vehicles 1 2l gasoline 1 25l gasoline 1 4l gasoline 1 6l gasoline 1 8l gasoline 1 81 GDI 2 01 gasoline 2 5l gasoline 3 0l gasoline engineswith engineswith engineswith engineswith engines with gasoline engineswith engineswith engines w2. assumed asa function of starting point from the city centre starting in zone A A A a E T he resulting excess particulate emission distribution asa function of distance from the town centre is shown in figure 9 AEA Technology Page 11 AEAT ENV R 0639 Issue 1 Figure 9 Simulated excess particulate emission as a function of distance from town centre 70 Excess emission g 3 g w a 20 0 1 2 3 4 5 6 Distance from centre km 4 3 EFFECT OF CHANGING THE NUMBER OF TRAFFIC LANES If the number of traffic lanes is changed the flow of traffic may be affected which will change the time taken to drive a set distance Asthe excess emissions are produced asa function of time for relatively short distances there could be a significant impact on the excess emissions produced This effect can be estimated using the model The model calculates emissions asa function of driving time and not distance The driving time is calculated from the distance and assuming a constant average speed of the ECE cycle used to measure excess emissions N o real life stuation is going to exactly reflect this drive cycle so the calculated excess emissions are representative of urban style driving However relative changes may be predicted so that if a lane change produces a 20 increase in average speed for example then the journey time decreases by 20 Asthe average speed used by the model cannot be changed the user can simulate this circumstanc
3. comparative schemes analysed is likely to remain valid T he equations used to model the excess emissions were determined from experimental data as part of aUK DETR funded project The summary report of the project has the following reference DCW Blaikley AP smith EA Feest and AH R eading UG 219 TRAMAQ Cold start emissions Summary report AEA Technology report no AEAT EN V R 0638 M ay 2001 which can be obtained electronically from http www aeat co uk netcen airqual research reports 2 Loading the model T he model has been incorporated into aM icrosoft Excel spreadsheet The user uses a mouse to click on menu buttons which run macrosto enable access to the different areas of the model T he model calculations are based on the equations outlined in Appendix 1 T he calculations are hidden from the user and occur instantly when any user input parameter has been changed The user should either double click on the file name EX EM PT X LS within W indows explorer or open the file from within Excel The file isa Microsoft Excel 97 workbook The user will be prompted by Excel to enable the macros Click on the Enable M acros button A password prompt will then appear T he workbook is protected from being accidentally corrupted by a set of passwords T he user should click on the R ead O nly button On opening the spreadsheet the appearance of Excel will be changed by macros within the spreadsheet removing scroll ba
4. emission kg Excess particulate emission g Distance from car park km The model can smulate many different car parking arrangements For example the parking time might be different if the car park is for a shopping centre a distribution of parking times could be used T he vehicles may not arrive in ahot condition so that the excess leading to the car park has to be included in the calculation T he vehicles may not all drive beyond 5km from the car park etc T he change with time of day could be mulated with changes in vehicle number and ambient temperature 4 2 EXCESS EMISSIONS AS A FUNCTION OF DISTANCE FROM A TOWN CENTRE T he model calculates the total excess emissions produced from a specified set of conditions there isno information given about the spatial or time distribution of these emissions H owever by careful use of the model this data can be extracted For example let us consider arbitrary radial zones surrounding a city centre at 0 1 2 3 up to 7km from the city centre as an example labelled as zones A to H respectively For mplicity of explanation we will assume that vehicles only drive into the city centre itself W e can calculate the excess emissions produced in each zone on driving into the city by using the following procedure InDATA ENTRY sheet we will use just stage 1 so set the time and distance parameters of stages 2 and 3 to zero Then with the appropriate temperatures set the distance tra
5. 3 3 5 1 5 o P N AEA Technology Appendix 1 Page 2 AEAT ENV R 0639 Issue 1 Pollutant_ Te lo a q a au amp Renault Laguna 1 8l A A eS Oe A AAA 00 ales li po Oe 0 Re e pame om 1 asa 3 ue om po ms os 1 zoo 3 o o Om 2 O rara gt gt gt Ford Fiesta 1 251 eo p RED JE a E A A 0 027 PO a a 3 5x10 Toyota Avensis 1 8 o A a fe mo w o 4oao7_ 2 ws 0 a a Honda Civic 1 41 fee a AAA a te Oe i ee Ee o AEA Technology Appendix 1 Page 3 AEAT ENV R 0639 Issue 1 Pollutant Peugeot 206 1 21 EE A A RA AVE MEA a a A AE E Ce E Parameters to calculate T p a DT ambient IN ETS CO ld VW Golf 1 9 Tdi diesel Vauxhall Vectra estate L81 PC O Vauxhall Omega auto 25 o __ 6 ____0A Mitsubishi Carisma 16 AEA Technology Appendix 1 Page 4 AEAT ENV R 0639 Issue 1 7 Parameters for the time evolution of excess emissions F 1 exp bt where F isthe fraction of total excess emissions produced after time t Vauxhall Vectra estate L8 00025 oonan 00045 0008 AEA Technology Appendix 1 Page 5 AEAT ENV R 0639 Issue 1 8 Heating and cooling parameters For the vehicle heating profile T T c t 1 c 47 until t t gt t or T T gt T when T T T The value of t is dependent on the vehicle start temperature and is calculated by solving the eq
6. AEAT ENV R 0639 Issue 1 UG219 TRAMAO Excess emissions planning tool EXEMPT user guide AP Smith M ay 2001 AEAT ENV R 0639 Issue 1 UG219 TRAMAQ Excess emissions planning tool EXEMPT user guide AP Smith M ay 2001 AEAT ENV R 0639 Issue 1 Title UG219TRAMAQ Excessemissions planning tool EX EM PT user guide Customer DETR Customer reference PPAD 9 99 6 Confidentiality Copyright AEA Technology plc copyright and All rights reserved reproduction Enquiries about copyright and reproduction should be addressed to the Commercial M anager AEA Technology plc T he views expressed in this report are not necessarily those of the DETR File reference DD 89927 Report number AEAT ENV R 0639 Report status Issue 1 AEA Technology plc Engines and Emissions 401 8 H arwell Laboratory H arwell Didcot O xfordshire 0X110Q Telephone 01235 434422 Facsimile 01235 436322 AEA Technology isthe trading name of AEA Technology ple AEA Technology is certificated to BS EN 150 9001 1994 Name Signature Date Author AP Smith Reviewed by EA Feest Approved by DCW Blaikley AEA Technology ii AEAT ENV R 0639 Issue 1 Contents 1 Introduction 1 2 Loading the model 2 3 Using the model 3 3 1 MAIN MENU 3 3 2 INFORMATION 3 3 3 DATA ENTRY AND RESULTS 3 3 4 ADVANCED MENU 5 3 4 1 Vehicle parc definition 5 3 4 2 Detailed results 6 3 4 3 Graphs menu 7 3 4 4 HELP 9 3 5 QUIT 9 4 Scenarios 9 4 1 EXC
7. ESSEMISSIONSASA FUNCTION OF DISTANCE FROM A CARPARK 9 4 2 EXCESSEMISSIONSASA FUNCTION OF DISTANCE FROM A TOWN CENTRE 10 4 3 EFFECT OF CHANGING THE NUM BER OF TRAFFIC LANES 12 Acknowledgements 13 Appendices APPENDIX 1 MODEL PARAMETERS AEA Technology iii AEAT ENV R 0639 Issue 1 1 Introduction M odelling the emissions from vehiclesis becoming an increasingly important activity in planning the environmental impact of future urban developments T hisis largely done using emissions factorsfor vehicles based on their level of emission when being driven at their normal operating temperatures H owever in urban environments vehicles are usually started under engine conditionsthat are different to the hot operating conditions The emissionsfrom these vehicles can be very different to those calculated using the basic emission factors T his model seeks to address this issue and calculates the extra emissions that are produced when vehicles start from more realistic starting conditions T he results from this model may be used in conjunction with results from a traffic based emissions model that calculates mass emissions on a road network from vehicles with their engines at normal operating temperature These may come from models combining traffic based emission factors in g km available from the N ational A tmospheric E missions Inventory http www aeat co uk netcen airqual index html and the national emission factor database with vehicle
8. e by reducing the travelled distance by 20 and calculating excess emissions For example consider 1000 vehicles driving 4km along a road at an average speed x kph The journey time for case 1 is then y hours If the number of traffic lanes is reduced we may get a 25 reduction in average peed which isnow 3 implying ajourney time of 1G for case 2 But for the purposes of the model the speed is unchanged it actually assumes a constant average speed of 18 4kph at x kph Therefore we must adjust the distance travelled in the model to give the correct journey time i e the effective distance travelled isnow 10 km If we assume an ambient temperature of 0 C a tart temperature for stage 1 equal to the ambient AEA Technology Page 12 AEAT ENV R 0639 Issue 1 temperature parking for 3 hours and equal drive distances in stages 1 and 3 of the model we get the following results ExcessCO Excess CO Excess Exces NO Sar kg kg THC kg kg Cael 448 571 467 0 93 et 2 e 55 A 4 A 98 EE 6 reduced traffic lanes T here is clearly a substantial increase in excess C O emissions produced by this smulated reduction in traffic lanes but the other emissions are largely unaffected with particulate excess actually reducing slightly T hisis because although greater excess of particulate will be produced on the stage 1 journey for case 2 as the journey time is longer the engine will get hotter and th
9. ed in detail T he results are presented on a stage by stage basis for each individual vehicle type For the two driving cycles the excess emission per vehicle for each vehicle type is listed together with the total when integrated over all vehicles T he final vehicle temperature is also given after driving and parking The resultsin Figure 5 are obtained using the data listed under DATA ENTRY and VEHICLE PARC AND DRIVE CYCLE listed earlier AEA Technology Page 6 AEAT ENV R 0639 Issue 1 Figure 5 Detailed results screen TOTAL EXCESSEMISSION all vehicles g CO co THC NOx Particulate VEHICLE pemes SY RAR O Sa say 13 1 21 gasoline engines with catalyst 25553 64235 380 20 7334 1257 gasoline engines wi cata A 2 03 ee ae Ce IC eh III INES 18 gasoline engineswith catalyst i Sd aS YT 13 FLaIGDT gasoline engineswith cay RR E EEE E E A A _____ __ _ a gt gt 257 gesoine engines win cayo A gt e ma 24 gas engin wp ir ert af rt III TOTALS EST 268010 3 45125 8 3560 3 381 9 44 6 Pies vices POP rs 21 geome eng wT ay O sp ssf mn gt TT IZ 1 6 gesofne engines wth catalyse ES 2 E af a GD canine engnesath eas a rot rt st or 20 gasoline engineswith cata S E E E T 32 iF 7ST gasoline engines with catalyst 8H 3 3 01 gasoline engines with catalyst 33732 ONO ICAO ANO NEO WEI se fs NES TOTALS A a Dre vendes NANA O 00 1 21 gasoline engines with catalyst 8 53ST 0 006
10. emission given by diesel and catalyst gasoline vehicles N o account is taken of non catalyst gasoline engines In the current 1999 vehicle parc non catalyst gasoline vehicles comprise 44 of the total number of vehicles predicted to fall to 6 by 2005 By assuming all gasoline vehicles have catalysts we will be overestimating the total excess emissions the overestimate decreasing asthe number of non catalyst vehicles decreases AEA Technology Page 5 AEAT ENV R 0639 Issue 1 T he reason for this overestimate is the fact that excess emission is relative to hot emission Consider an engine that is fitted into two vehicles one with vehicle A and the other without vehicle B acatalyst Assuming both engines produce very nearly the same levels of pollutants when hot vehicle B will emit less due to the effect of the catalyst W hen both vehicles are cold the engines will produce extra emissions above their hot start emissions T he catalyst will not be at operating temperature during most of this period and so both vehicles will give smilar emissions T hus relative to the hot start emissions vehicle B will produce a higher excess emission Clicking on lt R ETU R N gt takes the user back to the ADVANCED MENU Figure 4 Vehicle parc definition RETURN PRINT AEA TECHNOLOGY THE INNOVATION BUSINESS 3 4 2 Detailed results Clicking on lt DETAILED R ESU LT S gt gives access to the sheet where all of the results are display
11. erefore will be warmer at the start of stage 3 which will produce less excess than for case 1 T he overall excess change will therefore be very dependent on parking time and ambient conditions 5 Acknowledgements T he author is grateful to Eric W yatt of the DETR for his support and encouragement during the project The AEA Technology s Engines Emissions team for the provision of experimental data Tim M urrells John W atterson John Abbott and Beth Conlan of AEA T echnology s Environment NET CEN Division for their advice on the application of the model to air quality modelling The Local Authorities who gave of their time to discuss this work and its relevance to them and to suggest improvements to the model AEA Technology Page 13 AEAT ENV R 0639 Issue 1 Appendix 1 Model parameters CONTENTS 1 Parameters for calculating excess emissions 2 Parameters for the time evolution of excess emissions 3 H eating and cooling parameters AEA Technology Appendix 1 Page 1 AEAT ENV R 0639 Issue 1 6 Parameters for calculating excess emissions W hen AT lt T py Xs a AT a AT otherwise Xs a a AT where AT Thor To To Start engine oil temperature Te H ot engine oil temperature T o a bT mus All temperatures are in C VW Golf 1 91 Tdi diesel co gt T o o S BS f o ll Ali Al o o ceo ESE E E J a i aas E e o eoe PES E A A E A E G _ po vw o 684 5 O N N N 2 5
12. ith catalyst catalyst catalyst catalyst catalyst engines with catalyst catalyst catalyst catalyst Vehicle type AEA Technology Page 8 AEAT ENV R 0639 Issue 1 3 4 4 HELP Clicking on lt H ELP gt accesses the sheet shown below which gives a imple summary of instructions on how to use the model 3 5 QUIT Clicking on lt QUIT gt from the main menu will close down the model and restore E xcel settings to include the formula bar scroll bars etc The user will be prompted to ensure they want to quit 4 Scenarios 4 1 EXCESS EMISSIONS AS A FUNCTION OF DISTANCE FROM A CAR PARK T he model can be used to calculate the distribution of excess emissions as a function of distance from a car park T here will be excess emission due to the fact that the vehicle engine temperatures will have cooled during the parking time For example let us assume that all vehicles arrive in the car park with their engines hot producing no excess emission in the surrounding area on the way to the car park If the car park was attached to a sports complex we might assign a parking time of 100 minutes Thistime would vary depending on the car park application W e will also asume a total of 1000 parked vehicles during acold winter s day with an ambient temperature of 0 C In order to ensure that the vehicles arrive hot we set the stage 1 distance to a high value say400km with a start temperature of 50 C and ambient temperature of 0 C However this i
13. kilometres travelled on the road network Alternatively they may come from other air quality and emission estimation procedures for example the Highways Agency DM R B procedure D esign M anual R oads and Bridges V olume 11 Section 3 Environmental A ssessment T echniques Part 1 Air Quality M arch 2000 where the user inputs traffic flows on specified road links to calculate emissions and air concentrations near the road sde T he user can then add the impact of excess emissions from starting vehicles in an area to the hot exhaust emissions calculated This might be useful for a scheme appraisal for example a car park or out of town shopping complex where many cars will starting their journeys with cold engines The excess emissions calculated by the model are based on the measurements from a sample of 2 diesel and 13 petrol cars fitted with three way catalysts T he results from the model are weighted according to the proportions of the sampled car types in the national fleet in 1999 not in terms of the model types but in terms of fuel type petrol and diesel and engine capacity N ote that no account is taken of excess emissions from non catalyst gasoline engines In the current 1999 petrol car vehicle parc non catalyst gasoline vehicles make up 44 of the total number of vehicles predicted to fall to 6 by 2005 By assuming all gasoline vehicles have catalysts the model somewhat overestimates the total excess emissions the overe
14. nitial stage will produce some excess emission that we do not wish to include in the calculation Therefore the distance for stage 3 should initially be set to zero so that the model calculates the excess emission from stage 1 T hese values should then be subtracted from all subsequent calculated values W e set the time for parking in stage 2 as 100 minutes and the start of parking temperature as 999 so that the model usesthe calculated hot engine temperature from stage 1 The ambient temperature is set to 0 C for all three stages In stage 3 we set the start engine temperature to 999 so that it is calculated from the rate of cooling in the car park W e then allow the model to calculate the excess emission asa function of distance for example at 0 5km intervals up to 5km The excess emission produced in stage 1 has to be subtracted from all of the data calculated as a function of distance from the car park T he excess emission produced at each distance from the car park isthen calculated by subtracting the sum of all the excess produced up to that point For example the total excess emission produced at a distance of 3km would be the total excess AEA Technology Page 9 AEAT ENV R 0639 Issue 1 produced by driving 3km minus that from driving 2 5km In thisway the distribution shown in Figure 8 isobtained Figure 8 Excess emission of CO and particulate as a function of distance from a car park CO s Particulate Excess CO
15. obtained using the default vehicle parc see Section 3 4 1 below AEA Technology Page 4 AEAT ENV R 0639 Issue 1 By clicking on lt PR INT gt the sheet will be printed Clicking on lt MAIN MENU gt will return to the main menu N ote that the model can be used to calculate the emissionsfrom a single stage by setting the time of stage 2 to zero and the distance of stage 3 to zero 3 4 ADVANCED MENU Clicking on lt ADVANCED MENU gt gives the user access to more detailed analysis facilities T here are five options available in this menu including returning to the main menu Figure 3 Advanced menu screen Excess emissions planning tool Advanced M enu VEHICLE PARC GRAPHSMENU RETURN TO AEA TECHNOLOGY THE INNOVATION BUSINESS 3 4 1 Vehicle parc definition Clicking on lt VEHICLE PAR C gt accesses the sheet where the distribution of vehicle types is defined T here are currently 10 different vehicle classficationsin the population and the percentages of each should be set to represent the overall vehicle population distribution The total percentage should be 100 exactly otherwise error warnings will be printed in other areas of the model Figure 4 shows the vehicle parc definition screen together with the default settings These are based on the national fleet in 1999 figures not in terms of the model types but in terms of fuel type petrol and diesel and engine capacity N ote that the model predicts excess
16. oxide CO kg 448 3 Carbon monoxide CO kg 57 10 STAGE 2 PARKING Ambient temperature C Parking start oil temperature C T otal unburned hydrocarbons kg 4 67 Parking time minutes O xides of nitrogen NO kg 0 93 STAGE 3 DRIVING Ambient temperature C Particulates g 63 84 AEA TECHNOLOGY Vehicle start oil temperature C Driving distance km Drive cycle type MAIN MENU PRINT T he user enters the total number of vehicles in the smulation followed by the information for stage 1 driving ambient temperature start engine temperature driving distance and drive cycle type The drive cycle type must be a number between 1 and 9 inclusive A list of options will appear when entering data in this cell In the present model only one drive cycle is incorporated the multiple ECE urban cycle tested in this work The other options have been incorporated for possible future upgrades of the model THE INNOVATION BUSINESS After the initial driving a parking stage is incorporated which models the cool down of the vehicle T he start vehicle temperatures can be set manually or the model will calculate them automatically from the heating profile of the first driving stage if the user enters 999 The final driving stage is similar to the first except that the start engine temperature can either be set manually or calculated by the model from the parking i e cooling stage T he screen above is
17. rs formula bars etc AEA Technology Page 2 AEAT ENV R 0639 Issue 1 3 Using the model Thissection will describe the user operation of the model and the results given 3 1 MAIN MENU The opening sheet of the model the main menu has four options as per the picture below Clicking on any of the buttons will either take the user to a new sheet or quit from the model Figure 1 Main menu sheet Excess emissions planning too INFORMATION DATAENTRY ae AND RESULTS Y ADVANCED MENU ay QUIT AEATECHNOLOGY THE INNOVATION BUSINESS 3 2 INFORMATION Clicking on lt INFORMATION gt loadsa screen which gives a brief description of the model and its purpose The user returnsto the main screen by clicking on the only button on this sheet 3 3 DATA ENTRY AND RESULTS Clicking on the lt DATA ENTRY AND R ESU LT S gt button accesses the sheet see picture below in which the user enters the information relevant for the smulation to be performed and AEA Technology Page 3 AEAT ENV R 0639 Issue 1 the total excess emissions of each pollutant integrated over all vehicles and all three stages is displayed The simulation is split into three stages 1 Driving 2 Parking 3 Driving Figure 2 DATA ENTRY AND RESULTS sheet T otal number of vehicles 1000 TOTAL EXCESS EMISSION STAGE 1 DRIVING Ambient temperature C Vehicle start oil temperature C Driving distance km Drive cycle type Carbon di
18. stimate decreasing asthe number of non catalyst vehicles decreases in future years It should be noted that the model is based on excess emissions from cars with Euro 2 engines It is likely that these excess emissions will decrease for new catalyst carsin the future as the new European emission standards Euro 3 and Euro 4 start to kick in from 2000 T hisis because car manufacturers will need to reduce emissions during the engine start up phase of the drive cycle to satisfy the more stringent regulatory type approval limit values T hisislikely to be achieved by reducing catalyst light off time the time it takes the catalyst to reach a temperature at which it becomes effective for example by pre heating or locating the catalyst unit closer to the exhaust manifold AEA Technology Page 1 AEAT ENV R 0639 Issue 1 Estimating how much such new technologies will reduce the excess emissionsis not trivial and is beyond the scope of the current model design requirements The model could however be updated to include the impact of the evolution of the technologies should the necessary experimental input data become available By excluding the impact of new technologies on excess emissions from the fleet in future years as well as the excess emissions from non catalyst cars the model will always tend to be overestimating the contribution of excess emissions to the overall emissions calculated for a particular scheme H owever the ranking of
19. uation T T c t c t so that t C c 4c T T 26 For vehicle cooling 256 7 7 ay T T where T isthe temperature at time zero i e at the start of cooling See ms k gt 4010 4 44107 Vauxhall Vectra estate 18l 3 44x10 4 0x10T 95 5 0 887 0 0033 Mitsubishi Carisma 1 8 GDi 4 05x10 2 5x10 T 87 0 83T 0 0035 Peugeot 306 1 9 estate Hdi diesel 3 71x10 4 07x10 Ta 88 T 0 003 Vauxhall O mega auto 2 51 3 33x10 4 63x10 Ta 93 6 0 48T 0 0023 Renault Laguna 1 81 3 00x10 3 00x10 Ta 91 5 0 86T 0 0035 Ford Fiesta 1 251 3 80x10 2 60x10 T 86 1 0 56T 0 0035 Vauxhall Corsa 1 21 3 00x10 1 70x10 Ta 87 3 0 671 0 0035 Mitsubishi Carisma 1 61 4 30x10 1 29x10 T 90 5 0 65T 0 0038 Toyota Avensis 1 81 3 76x10 6 06x10T 88 5 0 797 0 0035 Honda Civic 1 41 4 48x10 4 51x10 T 95 1 0 80T 0 0035 Skoda Fabia 1 4 3 18 10 5 93x10T 98 2 0 927 0 003 Ford Mondeo 2 01 6 50x10 1 20x10 T 103 0 84T 0 004 Peugeot 206 1 21 2 60x10 87 1 0 847 0 0038 Jaguar S type 3 01 5 47x10 3 70x10T 95 9 0 897 0 0024 AEA Technology Appendix 1 Page 6
20. velled to 1km and note the excess emissions for 1 vehicle total vehicles set to one Calculate the same AEA Technology Page 10 AEAT ENV R 0639 Issue 1 for each kilometre travelled up to 7km Then starting at zone H the total excess produced in G isthe total number of vehicles starting in H multiplied by the excess emission from 1km driving T he excess produced in zone F by vehicles starting in H isthe difference in excess between 1 and 2km of driving multiplied by the number of vehicles starting from H and driving 2km This procedure is repeated all the way into the city centre The same isthen done with the vehicles starting in each zone in turn until in zone B all vehicles travel 1km into zone A The total excessin each zone is then integrated from each starting point N ote that this can be made even more complex by defining different vehicle parc distributions at different zones perhaps reflecting different wealth in each area Also the return journey parameters can also be calculated by initially following the above procedure and then subsequently adding a cooling and driving home stage the stage 3 excess emissions being calculated from the difference to the above calculation Asan example we have assumed a vehicle start temperature equal to the ambient temperature of 0 C and that vehicles drive in only one direction into the city centre i e the return journey has not been modelled The following distribution of vehicles has been
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