Evaluation of in-car speed limiters – Final report

Författare

Andras Varhelyi
Samantha Comte
Tapani Mäkinen

Summary, in English

This document describes the field- and driving simulator experiments carried out within Work-package 3.2 (Evaluation of in-car speed limiters). In both the field study and the simulator experiment positive effects of the speed limiter were found in terms of large speed reductions (particularly in urban areas), reduced speed variance and better speed adaptation on critical places (approaches, curves and areas with vulnerable road-users). On the other hand, both studies found negative behavioural adaptation effects too. However, while the simulator experiment indicated less safe car following behaviour at all speed levels, the field study showed that following behaviour became safer at speed levels below 50 km/h. The simulator trial showed additional negative effects in form of behavioural adaptation when driving in fog. However, the indicated complacency and loss of vigilance in fog arose with the so called “fixed speed limiter” (which is adjusted to the actual speed limit) can be avoided with a dynamic system which adjust the speed limit to the actual conditions (the dynamic system performed well in this aspect). Other negative effects in terms of higher speeds in turns or deteriorated giving way behaviour, found in earlier experiments with speed limiter (Persson et al 1993), could not be corroborated by the findings from the field study. In terms of driver mental work load the field study showed increased frustration while the simulator experiment could not display any effect. While the simulator study did not show significant effects on travel time the combined data from three countries in the field experiment showed a small, but statistically significant increase. The main conclusion is that automatic speed limiting by an in-car equipment is promising within built-up areas. The acceptance of the system amongst drivers is the highest there. On the other hand, data from rural conditions was scant and there was not much free driving on rural roads involved in the study.

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