Computer exercise 2 – Description
Contents
1. is the harmonic mean speed in km h The harmonic mean speed also known as the space mean speed for a section is the travel mean speed e hspd2 is the deviation of the space mean speed e ttime1 is the travel time in seconds The definition of the different tables and columns can be found in Appendix 2 in the AIMSUN v4 2 User Manual The manual is available under s GETRAM manualer Page 4 7 Task 1 Simulation of network 1 2 and 3 Conduct simulations of the networks corresponding to task 1 3 in computer exercise 1 Remember to save the results in different database files Answer the questions below using statistics from the second half hour period i e 7 8 Network 1 Turn proportions 1 How large is the traffic flow the average travel time and the average speed on the following sections Section Flow Travel time s Speed km h 4 10 11 12 2 How large is the total flow in the system Answer vehicles h 3 How long is the average travel time in the system Answer seconds 4 How high is the average speed in the system Answer km h 5 How many vehicles turns left from section 10 Answer vehicles Network 2 OD matrix 1 How large is the traffic flow the average travel time and the average speed on the following sections Section Flow Travel time s Speed km h 4 10 11 12 2 How large is the total flow in the sys2. ITN LINKOPINGS TEKNISKA HOGSKOLA TNK082 Johan Janson Olstam amp Andreas Tapani 1 28 08 Computer exercise 2 Simulation in AIMSUN 2 Computer exercise 2 Description The computer exercise is an introduction to how to conduct simulations using AIMSUN 2 In this computer exercise the networks which were created in computer exercise 1 will be simulated and analyzed The aim of the exercise is to give basic knowledge on which settings that should or could be changed which statistics that can be gathered how to choose and interpret output data etc This exercise consists of 3 obligatory tasks The first task is to simulate the three obligatory networks from computer exercise 1 and answer questions about traffic flow levels average speeds etc The second task is to run several replications in order to study how well one replication represents the more representative average from several replications The third and last task is to test different route choice models and analyze how different models affect the result from the simulation Menu and tab choices will in this document be marked using bold font e g save the network File Save as Selection or marking of radio buttons or check boxes or writing values in edit boxes will be marked with italic font e g set the lane width to 3 5 meters by writing 3 5 in Lane Width Examination You have to solve ta
3. ate in order to start the simulation Note All replications are run in batch mode 1 Compare the average values from the 10 replications with the results from the replication with Seed 3871 Do the results from the 3871 replication deviate much from the average from the 10 replications Answer Task 3 Route choice All simulations so far have been conducted assuming that all vehicles choose the shortest route between the origin and the destination AIMSUN offers several options and models for vehicles route choices The route choices can either be modelled as a fixed or a dynamic choice Load Network 3 Change the route choice to fixed time instead of fixed distance in Experiment Route Choice Run the simulation 1 Did the vehicles route choices change Hint check the turn statistics for example for left turners from section 10 Answer Now change the route choice model to a Multinomial Logit model Let the cycle time be 5 minutes i e the shortest paths will be updated every fifth minute Let the number of intervals be 1 and set the capacity weight to 1 the higher value the higher punishment for paths with low theoretical capacity Choose Yes in the Dynamic drop down list Set Initial K Sps to 1 and Max number to keep to 5 Set Max number of Route to 3 Finally set the parameter 6 in the logit model to 10 Each vehicle will now choose their route according to the path they observe as the best wh
4. en they enter the network 2 Did the vehicles route choices change Answer 3 Do the route choices vary over time Answer Page 7 7
5. mulation one simulation step per button click e Batch simulation without animation The simulation can be stopped using Run Stop The simulation can be started again using any of the run alternatives To restart the simulation from the initial start time the simulation has to be reset by pressing the rewind button or Run Begin Results After a completed simulation the results can be viewed by opening one of the output text files or the database file It is recommended to save the data in a database file This makes it easier to view limited parts of the data and to copy it to other calculation programs as Excel or Matlab The database file includes several tables The following tables are of most interest during this exercise e SectSta includes information on flows travel times etc for the different sections e SysSta includes flows travel times etc for the whole network e TurnSta includes flows turn times etc for all turnings In the output text files the turn statistics is presented in connection with the section statistics Some of the columns in the database tables are sometimes difficult to interpret The following is a explanation of some of the columns e from is the start time of the statistics period in seconds 7 is equal to 25200 seconds after 0 e tto is the stop time of the statistics period in seconds 7 is equal to 27000 seconds after 0 e flow is the traffic flow in vehicles hour e hspdl
6. roids Then double click in the Color field and choose color by adjusting the color bars To color the vehicles by destination choose View Vehicle Colouring Destination It is also possible to color the vehicles by their next turning vehicle type etc Before running the simulation some settings regarding the driver behavior have to be changed Open Experiment Modelling and change the following settings e Under the General tab o Simulation Step 0 75 s o Reaction Time at stop 1 00 s o Queuing Up Speed 1 0 m s o Queue Leaving Speed 4 0 m s e Under the Car Following tab o Car Following Model 4 2 o Apply 2 lanes Car Following model mark o Number of Vehicles 4 o Max distance 100 0 m o Max Speed Difference 50 km h o Max Speed Difference On Ramp 70 km h e Under the Lane Changing tab o Percent Overtake 0 900 o Percent Recover 0 950 o On Ramp Model 3 3 Page 3 7 In order to be comparable the simulations of the different networks should be run with the same initial values in the random number generator Set the Random Seed number to 3871 in the dialog box Experiment Replications Simulation The simulation can be controlled either via the Run menu or via the media player buttons at the bottom of the window There are several different run options e Run simulation with animation The simulation speed can be controlled using the bar on the right hand side of the record button e Step stepwise si
7. sk 1 3 in order to pass the exercise Present your solutions to the supervisor at the end of the scheduled class Settings in AIMSUN 2 Start by open up the AIMSUN program there is a short cut on the start menu under program GETRAM v4 2 Load the network In order to simulate a network the network and corresponding Result Container OR OD matrix has to be loaded into AIMSUN Also public transport plans and signal controls if any has to be loaded Following is a description on how to load these different modules e Load the network File Load Network and then locate your network in the Directory drop down list e Load turn proportions Result container File Load Traffic Result and choose the created Container Mark the created state under States Choose exponential arrivals e Load the OD matrix File Load O D Matrix and choose the created OD matrix Choose exponential arrivals e Load the public transport plan File Load Public Transport e Load the traffic signal control File Load Control It is possible to save a certain combination of network OD matrix signal control etc in a scenario File Save Scenario Next time you want to open this setup is it sufficient to open the scenario File Load Scenario Statistics settings The results from a simulation in AIMSUN 2 can be illustrated in several ways It is possible to create reports directly in AIMSUN Reports Current Report Statistics It is also possible to save
8. tem Answer vehicles h 3 How long is the average travel time in the system Answer seconds 4 How high is the average speed in the system Answer km h 5 How many vehicles turns left from section 10 Answer vehicles Page 5 7 Network 3 Traffic signals 1 How large is the traffic flow the average travel time and the average speed on the following sections Section Flow Traveltime s Speed kmh 4 10 11 12 2 How large is the total flow in the system Answer vehicles h 3 How long is the average travel time in the system Answer seconds 4 How high is the average speed in the system Answer km h 5 How many vehicles turns left from section 10 Answer vehicles Comparison of the networks 1 Are the results for Network 1 and Network 2 equal Why Why not Should they be equal Answer 2 How does the introduction of traffic signals affect the performance of the Network Answer Page 6 7 Task 2 Several replications Load Network 3 Choose to run replications Experiment Replications mark multiple and write 10 in Number of replications and press the Create button How many replications that are needed when conducting a simulation depend on the desired significance level You can read more about how to calculate the needed number of replications in the AIMSUN manual in chapter 7 4 1 Calculation of the number of replications at page 166 Press Simul
9. the output data in a text file or in a database which is preferable If data is to be stored in a database copy the file getram_42 mdb from s TN K TNK082 Lab 2 to a suitable folder on your home directory To save the output data in a text file or in a database do the following Page 2 7 e Text file Experiment Output Output Location and choose To ASCII Files and a suitable directory e Access database Experiment Output Output Location and choose To Access Database and the copy of getram_42 mdb Now it is time to choose which statistics that should be collected and calculated Experiment Output Statistics Choose for example the following e Gather Statistics e Periodic set the Time interval to 30 minutes e Store output e System Sections and Vehicle Types under the General tab e All and Turns under the Sections tab Simulation settings The simulation should be run for the time period 7 Experiment Run Time Set Simulated Initial Time to 07 00 and Simulated End Time to 09 00 Set Warm up period to 30 minutes 00 00 9 There are also settings concerning the animation of the vehicles The vehicles can for example be given different colors depending on their destination Only possible when using an OD matrix In order to do that the different centroids have to be given different colors Open View Preferences and choose Centroid under Colors in the tree structure Click in the Enable column for all cent
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