The effect of altered road markings on speed and lateral position

A meta-analysis


Davidse, R.; Driel, C. van; Goldenbeld, Ch.




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The basic principle of a sustainably safe traffic environment is that the traffic system is maximally tuned to the capabilities and limitations of its users. The road network and road infrastructure are easy to understand and predictable, and more or less automatically elicit the required, safe behaviour. However, we only have some general ideas about what such an infrastructure should look like, and these ideas are hardly based on empirical evidence. Research has shown that marking is the most important road characteristic with respect to the recognition of the road types that are used in a sustainably safe traffic system, and hence to the speed at which one is permitted to drive on these types of roads. But that does not tell us what effects on speed are to be expected when we replace the current road markings by other markings. What we do know about the relationship between road design and road user behaviour, is often based on the results of small-scaled studies. For example, a group of researchers has used a before-and-after study to investigate the effect on the average driving speed of adding an edge line. On the basis of such small-scaled studies, it is often difficult to predict general effects. Such effects can only be deduced by performing a systematic literature review such as a meta-analysis. In this report, we describe the results of a meta-analysis on the effects of altered road markings on the speed and lateral position of motor vehicles. Several kinds of alterations were studied, such as applying an edge line to a previously unmarked road or to a road that was already marked with a centre line. First, we studied the general effects of these different kinds of road markings. Next, we focused on those alterations that correspond to replacing the current road markings in the Netherlands by the markings proposed for the three sustainably safe road categories (through roads, distributor roads and access roads). As far as the general effects of altered road markings are concerned, the results of this meta-analysis showed that adding an edge line or a centre line to a road that was previously unmarked leads to an increase in the speed driven and a shift of the lateral position towards the edge of the road. Both effects have been related to negative effects on road safety, the first one based on more evidence (Finch et al., 1994; Aarts, 2004) than the second one (Mäkinen et al., 1999). The actual effects on road safety are, however, not known, since accident data were not included in the studies on which this meta-analysis was based. With respect to the alteration of road markings as part of the implementation of a sustainably safe traffic system, this meta-analysis shows that up till now, very little research has been done on the effects of these alterations on road user behaviour. The only sustainably safe road type for which enough data was available, was the access road. The results of the experiments that have studied alterations in road markings that were relevant for this type of road, point into the direction of a small decrease (-2 kilometres per hour) of the mean speed driven.

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40 + 9


SWOV, Leidschendam