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Report numberRA-2008-119
TitleEffects of supporting road markings on driving behaviour: a driving simulator study
Subtitle
AuthorsJan Vanrie
Published byPolicy Research Centre for Traffic Safety 2002-2006
Number of pages28
Date19/02/2008
ISBN
Document languageDutch
Partner(s)PHL
Work packageOther: Behaviour
Summary

In answer to the question on how to elicit optimal speed behaviour, the current report investigated three systems: the currently used system in which a speed zone is determined by a repetition of C43-speed signs, and two new systems in which drivers in a 70km/h speed zone can be supported through the use of additional road markings. In these alternative systems, the speed zone is indicated by a specific road sign (F4a)  signalling the driver is entering a zone with a specific speed limit and an additional, periodic marking (every 50m) along the existing edge line: either a short line or the number ‘7’.

 

To investigate the possible effects on driving behaviour with these new systems, compared to the traditional system, participants were asked to perform several test drives in a driving simulator. Three virtual drives were created based on a single route, a slightly curved road with two lanes, consisting of several segments: a 90km/h segment, a first 70km/h segment, an intersection and a second 70km/h segment. The ‘Signs’ route simulated the traditional system (C43 speed signs at the 90-70km/h transition and a repeated sign following the intersection), while for both the ‘Numbers’ and the ‘Lines’ route the 90-70km/h transition was marked with the F4a sign, no sign was present after the intersection and road markings (‘7’ or line) were added throughout the 70km/h zone.
 

Participants were not explicitly informed about the function of the road markings in order to determine what the effect is of the mere presence of these markings and also to investigate whether they would be noticed and used by drivers without prior instructions.

 

The participants performed each of the three possible routes, once under conditions of low mental load (only the driving task) and once under conditions of high mental load (driving task simultaneously with a challenging math task). For each of the six drives of each participant both objective data on the driving behaviour (position along the route, speed and the lateral position) and subjective data (via a scale to measure mental effort) were registered.
 

Results confirmed the negative impact of increased mental load on both subjective (higher scores on mental effort) and objective (inadequate speed behaviour) measures. The three routes (Signs, Numbers, Lines), however, did not differ much with respect to actual driving behaviour. Although the classic speed sign was more effective than the sign indicating the speed zone at the transition point itself (i.e., decelerating started earlier and was faster), in the first 70km/h segment that followed no significant differences were found for mean speed, mean standard deviation of speed or mean standard deviation of lateral position (i.e., whether drivers keep a steady position on the road). There was a shift in the mean lateral position: with the additional markings participants drove on average closer to the midline than without the markings. The size of the shift, however, was minimal. Subjective data did also not differ for the three routes.

 

Compared to the traditional system in the Signs route, mean speed in the Numbers and Lines route was significantly higher in the second 70km/h segment, i.e., when drivers passed the intersection. In 15.8% of the Numbers and Lines routes the driver accelerated above 80km/h immediately following the intersection (compared to 1.6% in the Signs route). This confirms the need for a support mechanism when explicit information on speed limits, like a repeated sign in the Signs route, is missing. This also indicates that, without prior information, the mere presence of the road markings does not elicit optimal speed behaviour. The markings themselves were not readily detected and the number ‘7’ was hardly ever recognised. 

 

Based on these results, we advise against a general implementation of the system of speed zones without an additional supporting system. Negative effects of the mere presence of additional road markings, lines or numbers, were not observed. However, for these markings to become effective, drivers will at least need to be thoroughly informed as to their function.

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