Headway performance in the University of Twente driving simulator: a validation study
The University of Twente (UT) owns a driving simulator for driving research. As driving simulators are an artificial environment, different from driving on a public road, the question of its similarity to the real world – it’s validity – arises.
This research aims to answer the question whether there is physical and behavioural similarity between the UT driving simulator and an instrumented vehicle in the headway attainment and keeping domain.
A test on the physical validity found that the angular size of a virtual lead vehicle at certain distance is on average 32.2% smaller than that of a real lead vehicle seen from a test vehicle. This leads to questions on whether there is a difference between how test participants perceive distance to the lead vehicle in the simulator and on the real road; and whether they will behave to headway instructions in a different way in those two vehicles.
This research on physical validity led to hypotheses on the difference in headway choice between simulator and instrumented vehicle; in headway choice at different speeds; in the time to attain the chosen headway; and in the headway keeping performance.
To test the behavioural validity, tests were performed with 22 participants. Each got into the UT driving simulator and was instructed to attain a certain headway to a lead vehicle, then keep that headway for 15 seconds. The headway instructions were given either in metres or in seconds, at different speeds of the lead vehicle. The same participants also took the same tests in an instrumented vehicle on a public highway. Data on the headway to the lead vehicle was continuously recorded. The recorded data was then tested with a series of repeated-measures ANOVAs on differences between simulator and instrumented vehicle headway data. No significant main effects on the type of vehicle were found, but there was an interaction between speed and vehicle on the time participants needed to attain an assigned headway. We suspect this difference can attributed to differences in other vehicle’s traffic behaviour between the simulated and public highways.
This leads to the conclusion that the University of Twente driving simulator is valid in the headway attainment and keeping domain with regard to the time headway chosen by participants and the headway keeping performance.