Run-Off-Road Collision Avoidance Countermeasures Using IVHS Countermeasures

Transcription

t’uU.S. Departmentof TransportationNationalHighwayTraffic SavingPeoplei’DOTHS808504September 1995Final ReportRun-Off-Road Collision AvoidanceCountermeasures Using IVHSCountermeasuresfTASK 4Volume 2: RORSIM Manual‘This document is available to the public from the National Technical Information Service, Springfield, Virginia 22161,

This publication is distributed by the U.S. Department ofTransportation, National Highway Traffic Safety Administration, in the interest of information exchange.The opinions,findings and conclusions expressedin this publication are thoseof the author(s) and not necessarily those of the Departmentof Transportation or the National Highway Traffic SafetyAdministration. The .Un.ited‘States Government assumes noliability for its contents or u&thereof. If trade or manufacturers’ name or products are mentioned, it is becausethey areconsidered essentialto the object of the publication and shouldnot be construed as an endorsement. The United StatesGovernment does not endorse products, or manufacturers.

ContractingThis report providesTechnicala basis for disseminatingtimely basis resultingreports are produced.support and/orOfficer’smodifyin the informationRepresentative’sthe preliminaryPreciscontract results on abeing available before the contract finalResearch performedduring the remainderof the contract maythe results, therefore, the material containedin this reportshould not be consider to be final. The current schedule calls for the completionresearch project by the third quarter of 1999.of this

This program was developedby Battelle for the U.S. Departmentof Transportation, National Highway Safety Administration aspart of Contract DTNH22-93-C-07023.Portions of the menu program are Copyright NationalInstruments Corporation. All rights reserved. NHTSA must notinstall more than five copies of the menu program without firstnotifying Battelle or National Instruments and, if necessary,paying a licensefee.Portions of the simulation program are Copyright I994 bySystemsTechnology, Inc. They are distributed with theunderstanding that they will be installed only on computers thathave a licensefor the proper version of KDANL from SystemsTechnology, Inc and a hardware key to run VDANL.

Technical Report Documentation 12.1. Report No.DOT HS 808 5044.Ciovemmcnl Accession No3. Recipients’s Catalog No.I5. R ortDateTitle and SubtitleSeptemberRun-Off-RoadCollisionAvoidance Countermeasures Using IVHS CountermeasuresTask 4 Report- Volume 2:RORSIM Manual6.5, 1995Performing Chganiration Code8. Performing Organization Repon No.7. Author(s)M. Koenig.D. Pane.D. PomerleauIO. Work Umt No. (TRMS)n code9. Performing organization Name and AddressRoboticsInstituteCarnegie Mellon University5000 Forbes AvenuePittsburgh,PA 1521311. Coneact of Grant No.DTNH22-93-C-0702312.13.Sponsoring Agency Name and AddressType of Report and Period Covered.NationalHighwayTraffic SafetyAdministration400 SeventhStreet,S.W.Washington,DC 20590FinalReport10-93to 9-9514. sponsoring Agency codeIS. Supplementary Notes16. AbstractThe Run-Off-Road Collision Avoidance Using IVHS Countermeasuresprogram is toaddressthe single vehicle crashproblem through application of technology to preventand/or reducethe severity of thesecrashes.This report documentsthe RORSIM computer simulation developedin Task 4. RORSIM isa PC program which simulatesthe combined effects of the dynamical propertiesof thevehicle, the responseof the driver, sensormeasurements,environmental conditions and invehicle countermeasuresystems. RORSIM is an extensionof the commercial programVDANL (Vehicle Dynamic Analysis NonLinear) which was developedby ScienceTechnology, Inc. (STI).This report is an operatingmanual that containsdetailed instructionson the operation ofRORSIM. Resultsobtainedusing RORSIM are containedin a companion volume, Task 4Volume I.17. KeywordsRun-Off-RoadCollisionAvoidanceSingle VehicleRoadway DepartureRORSIMOperatingManual19 security Cla?.if (of this repon)UnclassifiedForm DOT F1700.7 (8-72)20.Securiry Cl&f(of this page)18. Distribution StatmxntDocumentis availableto the public ngfield,VA 2216121.No of PqaUnclassified22. Price40 anoendicesReproductionof completedpagel ulhorizcd 621,184

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TABLE OF CONTENTSPageExecutiveSummary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .l1.0Introduction .1.1 RORSIM Software Overview .1.1.1 MenuInterfaceProgram .1.1.2 Dynamic Simulation Program . :. .1.1.3 Post-processorProgram .1.2 Purposeof the Model .Organization of this Manual .1.3.2.2.2.3.3.42.0Dynamic Simulation Software Description .Interfacing Enhancementsto VDANL .2.1InputParameters .2.2Simulation Features .2.32.3.1 Vehicle SpeedControl .2.3.2 Roadway .2.3.3 Simulation Termination .2.3.4 Driver Deadband . .' .Driver Inattention .2.4CountermeasureSystems .2.5.5.5.7.7.7.7.8.8.93.0MenuSystem .StartingtheRORSIMMenu .3.1MainMenu.ll3.2Vehicle. .3.3RORSIMSubmenus.133.43.4.1 Roadway .3.4.2 Environmental Conditions .3.4.3 DriverType .3.4.4 Simulation Scenario .3.4.5 CountermeasureSystemType .ParametersNot Appearing on Menus .3.5RunningRORSIM .3.6.ll.; 111419.2 023.25.28.2 9OutputOptions.3Graphical and Numeric .4.1Post-Processing .4.22.32.3 44.0iii.13.

TABLE OF CONTENTS(Cont.)Page. .3 7Customizing .3 7TheMenuSystem .5.1.37The Simulation Program .5.2.References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405.0.Appendix A.A-lA-2A-3I A-4A-5. A-6L A-7Quick Start Instructions .Installing RORSIM .A Simple Simulation To Make Sure It’s Installed .How To ChangeParameter:Setting Up A Crash Simulation .-Saving Your ChangesAnd Running The Simulation .Viewing The Results .Advanced Features: Simulating A CountermeasureSystem .You’reReady! .A-lA-lA-lA-2A-2, . A-3A-3A-4.B- 1Appendix B .Menu Screens .Appendix C.Vehicle ParameterList .C-lAppendix D.Lists of Files .D-lAppendix E.Plotting Variables in RORSIM .';.Index :.iv.: .E-lI-l

LIST OF TABLESPageTable 2-lCoded Incrementsto the Warn VariablesWhen a CountermeasureSystem SensesDanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Table 3-lWheretoFindVariablesontheMenuSystem. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12Table 3-2ProtectedRoadway Files . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14Table 3-3ParametersInput on Roadway Submenu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Table 3-4Environmental Condition ProtectedFiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19I Table 3-5ParametersInput on Environmental Submenu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Table 3-6Driver Type ProtectedFiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21Table 3-7ParametersInput on Driver Type Submenu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 1Table 3-8Simulation ScenarioProtectedFiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . .23Table 3-9ParametersInput on Simulation ScenarioSubmenu . . . . . . . . , . . . . . . . . . . . . . . . . . . .23Table 3-10CountermeasureSystemProtectedFiles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Table 3-l 1ParametersInput on CMU Look Ahead (TTD)CountermeasureSystemSubmenu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Table 3-12Parameterson CMU Look Down (TLC)CountermeasureSystem Submenu . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .,. . . . . . .26Table 3-13ParametersInput on CMU Curve WarningCountermeasureSystemSubmenu . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27V

LIST OF FIGURESFigure 3-lPlan of the Generic Roadway Used in ROSIM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Figure 3-2Sections of the Generic Roadway Used in ROSIM(Elevations are Greatly Exaggerated) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18Figure 3-3aCumulative Distribution of Steering Reaction Times(After Malaterre and lechner [ 19901). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22Figure 3-3bCumulative Distribution of Braking Reaction Times(After ‘Sivak [ 19821). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22vi

Executive SummaryIn support of the mission of the U.S. Department of Transportation’s National HighwayTransportation Administration @OT/NHTSA) to ensurethe safety of U.S. highway systems,theteam of CarnegieMellon University (CMU), Battelle and Calspanwas awardedcontract (DTNH2293-R-07023), “MIS Countermeasuresfor Run-Off-Road Crashes”. The overall objective of thisthree-phasecontract is to develop practical performance specifications for single vehicle roadwaydeparture(SVRD), or Run-Off-Road (ROR) crashavoidancesystems.PhaseI of the program was conductedover the period September 1993 to September 1995, with ascopeof “Laying the Foundation”. PhaseI consistedof the following four tasks:nnnnTask 1: Establish ROR crash subtypesand causalfactors by thoroughly analyzingthe crashproblemTask 2: Establish functional goals of candidate countermeasures based onintervention opportunities and mechanismsTask 3: Obtain basic operational, performance and functional data by performinghardware testing of existing technologiesTask 4: Develop preliminary performancespecificationsbasedon critical factors andmodels of crash scenariosAs part of Task 4, Battelle developeda sophisticatedcomputer simulation packagecalled RORSIM(Run-Off-Road SIMulation program) to predict the dynamic response of thedriver/vehicle/countermeasuresystemunder a wide rangeof operating,roadway and environmentalconditions. RORSIM is an extensionof the commercial code VDANL (Vehicle Dynamic AnalysisNonLinear), which was developedand is owned by ScienceTechnology, Inc. (STI) in Hawthorne,California.A key feature of RORSIM is a menu systemthat enablesthe user to “point and click” to establisha simulation scenario. Resultsof the simulation runscan be viewed with VDANL utilities, exportedto a spreadsheetformat, or exported to be displayed with a postprocessor. The postprocessorsupplied with RORSIM displays a plan view of the vehicle over a user-specifiedtime period. Astrobe-like depiction is created which shows the vehicles’s position and attitude at fixed timeintervals within the display period.RORSIM was used to support all of the PhaseI tasks,and particularly to support the developmentof preliminary performancespecificationsfor a Run-Off-Road countermeasuressystem. RORSIMwas designed to be a convenient and user-friendly analysistool for use by NHTSA engineersandothers involved in collision avoidanceresearch.This document is an operating manual that contains detailed instructions on the operation ofRORSIM. Results obtained using RORSIM are contained in a companion document, the Task 4Final Report Volume I. Quick start instructions for running RORSIM are in Afipendix A.

1.0 IntroductionThe RORSIM simulation packagewas developedas a tool for establishingpreliminary performancespecifications for Single Vehicle Roadway Departure or Run-Off-Road (ROR) countermeasuresystems. RORSIM can be used to estimate how effectively a countermeasuresystem can reduceROR accidentswhile maintaining an acceptablylow false-alarm rate.1.1RORSIM Software OverviewThe RORSIM simulation suite comprisesof three distinct programs: the menu interface programused to define a simulation scenario, the dynamic simulation program, and the post-processorprogram used to display results. All programs in the RORSIM simulation suite are DOSapplications.1.1.1 Menu Interface ProgramThe simplest way to begin defining a situation to simulate is through the menu program. Here thevariables that define what is going to be simulated are set. The speedof the vehicle, the design ofthe roadway, the weather,the sensitivities of the countermeasuresystems,the reaction times of thedriver, and many more valuesare selectedin the menu program. These values are savedin a seriesof disk files when you FILE then SAVE FILE on the main menu. When you select RUN! on themain menu, the menu program endsand calls the simulation program,RORSIM. RORSIM, in turn,reads all of the values that have been most recently selectedin the menu program and runs thesimulation. As the simulation is running, the program plots four output variables on the computerscreen. When the simulation is finished, other variablescan be plotted, or groups of variables canbe written to disk files for further analysis.While the menu interface program is normally used to call the simulation program, userswho aremore familiar with the program may also define a scenarioby editing the parameterfiles directly andthen immediately running the simulation program. All of the simulation input and output files areASCII text files, and can be modified with a text editor. Some of the parameter files cannot bemodified through the menu system;the only methodto modify them is with a text editor. The mostnotable files in this categoryare the vehicle parameterfiles, which can be selected,but not modified,in the menu program.1.1.2 Dynamic Simulation PromamThe dynamic simulation program‘ is an enhancement to the VDANL program, which is acommercial, general-purpose, rubber-tired vehicle simulation program owned by SystemsTechnology, Inc. in Hawthorne, California. The VDANL simulation allows modifications to itsoperation through the use of a USERMODULE program. Battelle’has developedthis program tocustomize VDANL for simulation of Run-Off-Road scenarios.P2

Many levels of detail are available for reviewing the results of a simulation. The simplest analysisof a single simulation is to look at the file MAXYPOS.DAT, which records the leftmost andrightmost positions of the vehicle’s front tires during the simulation. It is written at the end of everysimulation. This summaryof data is useful when comparing the results of many simulations, but itprovides no clues how the vehicle reachedthose positions. The best way to examine the events asthey unfold is to useVDANL’s own plotting capabilities,as describedin the VDANL Manuals andhighlighted in Section4.1, Graphical and Numeric Output Options. For more detailed analysis, thetime histories of one or more variables can be written to a text file and then imported to aspreadsheet,analyzed with a special-purposeprogram, or plotted with the post-processor. It isassumedin this manual that the user has accessto the VDANL manuals. Therefore, this RORSIMusers manual will focus primarily on understandingand using the features added by Battelle toVDANL.1.1.3 Post-nrocessorPromamA post processoris included with the RORSIM suite of programs. The trajectory of the vehicle overthe roadway can be plotted. The position of the vehicle is shown in plan view in severalpositionswith a fixed time interval betweeneachposition. The procedurefor producing the plots consists ofsavingthe required variablesfrom the simulation program, running a program to convert this outputinto a plotting format, and presentingthe data using AutoCAD.1.2 Purpose of the ModelThe primary motivation for developing the RORSIM simulation packagewas to provide a tool forestablishingpreliminary performancespecificationsfor Run-Off-Roadcountermeasuresystems.Theapproach used was to evaluatethe performance of severalproposedcountermeasuresystems andfrom those results derive performance specifications. Proposedcountermeasuresystemscan beanalyzed by several approaches(e.g., by implementation in actual hardware, by human subjectsoperating a driving simulator, and by desktop simulation of specific incidents). Each of theseapproachesprovides a different type of information.The main advantageof the RORSIM desktopsimulation is that the circumstancesof the scenariocanbe closely controlled and repeatedwith specific variations. Also, a scenariocan be simulated untila crash,which is not feasible for the actualhardware. During Phase1 of the Run-Off-Road project,RORSIM has beenusedfor studiesin which a key parameteris varied over a range to determine itseffect on the outcome of a particular scenario. RORSIM has also proven useful for performancetesting a vehicle in various near-emergencymaneuvers.Thesetestshaveprovided valuable data onyaw rates, lane closure rates, steering angles, and other parameterswhen roadway departure isimminent.

1.3Organization of this ManualThis manual contains instructions for using RORSIM, including the menu interface, dynamicsimulation, and the post-processor.Technical details are provided on how the model is configured,so users of the program can appreciateits limitations, capabilities, and can make enhancements.Derivations of the underlying formulas for the countermeasuremodels are provided in Volume I ofthis report [Pape, et al, 19951. The VDANL software is discussedin an earlier technical paperpreparedfor NHTSA by SystemsTechnology, Inc. [Allen, et al, 19921.Those who may use RORSIM to study the built-in proposed countermeasuresystems will findSections 3 and 4 of this volume most useful. These sectionscontain specific instructions for thescenario input and data output of the program. The installation and Quick-Start instructions inAppendix A will be helpful to all. Occasionalreferenceto Section2 may be necessaryto understandthe model’s capabilities. If you want to modify RORSIM to model newly conceivedcountermeasuresystemsor to model scenariosnot presently available, refer to Section 2 on program architecture,Section 5 on customizing, and the separate3-ring binder.Sufficient information on VDANL itself is presentedto develop skills in plotting and saving theresults. For complete details on VDANL, seeits online help file, VDANLHLP, and the VDANLuser’s manual [System Technology, Inc., 19891.I4

2.0 25Dynamic Simulation Software DescriptionThe dynamic simulation program, RORSIM, is an enhancementto VDANL. VDANL provides thevehicle dynamics model for the simulation as well as the closed-loop driver model. Battelle hasdevelopedenhancementsto VDANL for usein evaluating Run-Off-Road countermeasuresystems.These new capabilities include:nnn8nnnncrowned roadwayswith a banked curve,constant graderoadways,different roadway traction conditions,different sensorvisibility conditions,drivers with different driving capabilities,momentary driver inattention,ROR countermeasuresystemcharacteristics,andvarious driver reactionsto countermeasuresystemoutputs.This section.of the manual will discussseveralof thesefeaturesin further detail, allowing a deeperunderstanding of the model’s operation. Becausethis is mostly details of what goes on insideRORSIM, you can skip straight to Section 3.0 if you’re eagerto get going.2.1Interfacing Enhancementsto VDANLMost of the software code for Battelle’s RORSIM program is proprietary to STI, but the VDANLcode was customized through the use of an “Open Module.” When the program reachescertainlocations in its execution,called breakpoints,it invokes a function called USERMODULE, which hasbeen compiled and linked with VDANL.Each breakpoint provides an opportunity to modify an aspectof VDANL’s operation. For example,after VDANL has calculated the tire elevations and road surfaceproperties according to its owninternal procedure, it reachesthe Terrain breakpoint. If that breakpoint is activated, it calls theUSERMODULE function with the indication that it is currently at the Terrain breakpoint. Thefunction can then adjust the tire elevations to simulate a different terrain profile. Execution ofVDANL proper resumeswith the modified elevations.For a breakpoint to be active, it must,be“turned on” at the beginning of the simulation through menuselectionsin JQANL. BecauseRORSIM requiresseveralbreakpoints and will not work properlyunless all of them are turned on, VDANL should be run through the menu system or a macrowhenever RORSIM functionality is desired. All of Battelle’s enhancementsto VDANL were implementedusing the breakpoints. RORSIM usesseveralbreakpoints,including terrain, lane and curvatureerrors,initialization, and end of run. Mostof the actions are performed by code in the sourcefile UMROR.BAS, which has separatesectionsof code to handle eachbreakpoint. The calculationsof roadwayelevation and surfaceproperties are5

performed by a function in a separate source file, ROAD.BAS, which is called throughUSERMODULE. In addition, each countermeasuresystemcomprises two sourcefiles, one for thesensoractions, and one for the decision making actions. The countermeasureimplementation isdiscussedin greater detail in Section 2.5.The communication of variable values between VDANL proper and the user module is primarilythrough two large arrays, which are in a common block defined in USERMODJNC. One array,VARYY ( ) , contains the entire state vector of the system. It holds all of the variables listed inVDANLHLP, most of which are time-dependent. The other array, VDANLINP ( 1, contains theparametersread from FILES.DUM, which are essentially those that define the vehicle and driver.The RORSIM codereferencesquantitiesin thesearraysthrough subscriptsdefined in the include fileVDANLVARINC.For example, VARYY (yyPS1) is the 45th element in the variable list, theheading angle of the vehicle. Severalnew variables,specific to the needsof RORSIM, such as thecurrent TTD value, are also included in the VARfl ( ) array and defined in VDANLVARJNC. Thefunctions describingthe road, sensors,decisionmaking algorithms,and other Battelle-addedfeaturesare declared in the include file named RORSIMJNC.2.2Input ParametersAll of the simulation-specific parametersdefining a simulation are readby RORSIM from disk files,which are in ASCIl text format. The parametersrequired by VDANL itself are read from filesnamedin FILES.DUM. This includesthe entire definition of the vehicle. Thesefiles are read everytime VDANL begins a new simulation.After VDANL hasread the parameterfiles namedin FILES.DUM, it calls USERMODULE with theInitialize breakpointindicated. The USERMODULE directsreadingthe RORSIM-specific parameters.All of these source files, each corresponding to a page in the menu system, are opened byUSERMODULE. The parametersthat USERMODULE needsare read first. Then a special initializefunction in each sourcefile is called to read the parametersneededin that sourcefile.In the menu system, the parametersare organized according to operator preferencesregardingscenario input data. For example, dropout times for the sensorsare specified on the same menupage as the inattention times for the driver. This arrangementmakes it easy for the,operator toschedule a sensor dropout at about the same time the driver is not paying attention. The menusystemcreatesa file containing the parametersfrom eachmenu page. Each initialization functionfinds its own parameterswithin each file by searchingfor the line where the description of thefunction is enclosedin squarebrackets. For example, the roadway parametersin the road file andthe environmental surfacefile follow the line, [Road]. The functions in READFILES.BAS performthe task of fetching and parsing the parameterlines.The next to last line of each menu generated parameterfile is an indicator of whether the file is“protected.” If it is protected,the file is one of the standardset of pre-defined conditions providedby Battelle with the RORSIM package. The menu system will not change a protected file. (Of6

course, these files, like the other parameterfiles, are text files and can be modified by any texteditor.) The final line of each file is a verbal description of the conditions the parameters areintendedto model. This description is displayed in the menu program on the main menu when thefile is selected. Sample parameterfiles are listed in the accompanying3-ring binder.2.3Simulation FeaturesHere are brief descriptions of how some special effects are modeled in RORSIM.2.3.1 Vehicle SneedControlBecausethe slip generatedby the tires due to accelerationor braking affects the ability of the tiresto produce lateral forces for controlling steering, it was essential that the speedof the simulatedvehicle be controlled through the tires. Therefore,in the RORSIM program, the speedof the vehicleis adjustedthrough the throttle and brake pedals. The engine and drivetrain parametersused’in theRORSIM model are typical for sedans,but they do not attempt to model the specific performanceof a Ford Taurus. A simple speedcontroller was built in USERMODULE to actuatethe throttle andbrake pedals. The controller’s primary function is to hold the vehicle’s speed at the valuecommandedby the speedprofile file. When the driver is inattentiveto the vehicle’s speed,the speedcontroller takesno action at all. There is a provision for a driver to brake in responseto a surprise,even where that might not be an appropriate action. This situation is also handled by the speedcontroller, which does not alter acceleration or deceleration that might be applied by an activecountermeasuresystem.2.3.2 RoadwayBecause complete coordination between the road elevation, surface properties, and curvature isessential for modeling the behavior of the countermeasuresystems,the roadway properties arehandled entirely through the VDANL open module. A function in ROAD.BAS calculates theelevation and surfaceproperties of each tire according to the vehicle’s position and orientation ateachintegration step. The featuresthat can be modeledare describedin detail in Section 3.5, wherethe road menu page is presented. The instantaneousroad curvature for the driver model mustcorrespondto the vehicle’s position in the roadway. It is readfrom a separatefile than the roadway.To coordinate the two, the initialization function in ROAD.BAS createsa temporary file with thename TEMP#O@! . CRV, which has the curvaturefunction in the proper format for the driver model.2.3.3 Simulation TerminationWhen a vehicle departsits lane by more than a pre-determineddistance,it is deemedto havecrashed,and there is no point to continuing the simulation. The departuredistance is defined as the errorbetweenthe commandedand actual lateral lane position. The maximum tolerable error, yemax, isset in the .AUX file. Becauseit does not appearon any menu, the only way to changeit is to editthe file with a text editor. BecauseVDANL doesnot provide a method to terminate a simulation in7

the code, the simulation is stopped by applying an enormous force to the left suspension,whichupsetsthe vehicle and endsthe simulation. The last one or two data valuesrecordedfor a simulationthat endedin a crashareusually invalid. This method of terminating execution occasionally causesa BASIC error, which terminates the entire program. If the program abruptly crasheswhen thevehicle is far off the road, Yemax can be adjustedby one foot or so in order to fix the problem inmost cases. (A simulation can be stoppedmanually by pressingthe Esc key.)2.3.4 Driver DeadbandAn attentive driver does not exactly follow the lane center. There is a certain amount of variationin lane position due to minor disturbances and a human’s natural tolerance of small errors.Following the general approach of Carson and Wierwillie [1978], RORSIM has thresholds forheadingerror and curvatureerror. Errors below thesethresholdsare ignored. The threshold levelswere selectedso that the variancein lane position of a vehicle simulated in RORSIM traveling ona straight road is approximately the sameaspublishedvalues [Carson & Wierwille, 1978, Allen, etal, 19751. However, becauseRORSA4 does not have random disturbances,the bandwi

be written to disk files for further analysis. While the menu interface program is normally used to call the simulation program, users who are more familiar with the program may also define a scenario by editing the parameter files directly and then immediately running the simulation program.