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Completed project


FCW - Accelerated testing of Forward Collision Warning in heavy vehicles


Further information

Forward collision warning (FCW) systems alert the driver of an imminent rear-end collision with the vehicle ahead. FCW systems are difficult to test and evaluate in a real driving situation and a simulator study can thus be a feasible way of assessing various aspects of FCW systems, such as effectiveness and acceptance. A driving simulator allows for repeated exposure to critical situations, however, there is a risk that repeated critical situations reduce the realism and result in a change in driving behaviour. The aim of this study was to assess driving behaviour during non-critical parts of a driving session that contained repeated critical situations.

In a truck simulator 48 professional drivers participated in two driving sessions. The first session aimed at evaluating a FCW system which is reported elsewhere (classified). The second session was a 35 min long motorway drive with two critical and three less critical events. Between all events there was a car following situation. 32 of the drivers had a FCW system while the remaining 16 drivers had no FCW. Mean speed between the events, minimum distance to the vehicle in front in the car following situation, and performance on a secondary task - the arrows task - were used as measures of driving behaviour. In addition, the drivers answered a questionnaire about their driving behaviour.

The changes in driving behaviour after being exposed to repeated critical events were relatively small and did not increase/decrease with time. About half of the drivers stated that their attention and preparedness increased with time, particularly in potentially critical or suspicious situations, and there was a tendency towards increased distance to the vehicle in front. There was no difference between the FCW and the no FCW groups with regard to mean speed, minimum distance to the vehicle in front, and arrows task

The results from this study augur for the fact that accelerated testing in simulators is possible and that behaviour does not change in such a way that the results would be false or unrealistic. It should be noted that the study doesn't address how to handle possible learning effects associated with the FCW system itself and how the results (e.g. reactions to warnings) from repeated critical events should be analysed and interpreted.

Further research is needed in order to draw any general conclusions on if and how to use accelerated testing.


Project manager: Fredrik Stenson, Scania, +46 (0)8 553 503 24

Project partners: Scania and VTI


Reference: Fors, C., Hjälmdahl, M. & Hjorth, L. (2010). Accelerated testing of FCW for trucks - Part 2: Driving behaviour after exposure to repeated critical events. ViP publication 2010-5, Linköping: VTI, Sweden.

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