Recognizablility of Rural Roads in the Netherlands
L T Aarts, R J Davidse, SWOV Institute for Road Safety Research, NL
A recognizable road design is an important safety element in the Netherlands. This requires distinction between road types and self-explainingness of design features. SWOV examined the recognisability of roads and its effect on driver behaviour.
In the Netherlands, the Sustainable Safety vision is an important guide in improving road safety. In this vision, a central principle is ?predictability?. This principle builds on the idea that the road environment should conform to the expectations of road users in order to prevent errors that could lead to road crashes. These expectations are based on the characteristics of road types. We distinguish the following types of roads: access roads (30 or 60 km/h, vulnerable road users and agricultural vehicles possible, large amount of junctions), distributor roads (50 or 80 km/h, vulnerable road users separated from motorised traffic, no agricultural vehicles preferred, fewer junctions), and flow roads (100/120 km/h, no slow traffic, split-level junctions). Distinction of these road types and self-explainingness of their characteristics are requirements for recognizable roads.
To elaborate the predictability principle, 'essential recognition characteristics' (ERC's) have been defined. They consist of unique pattern of edge markings and lane separators per road type. Implementation of these ERC's has been started last years, especially on rural roads.
Although there were good reasons for these ERC's to be specified, there was little knowledge about the effects on road user behaviour and road user expectations. To find out, SWOV examined these topics in a photo-categorisation study and a driving simulator study.
In the first study, we examined the distinctiveness and self-explainingness of the different rural road types (15 photographs per road type) in various design options (ERC design and mix of ERC and traditional design): The study showed that road users had most problems with distinguishing the distributor roads from the flow roads. Possible explanations for this finding were that these roads differ particularly on edge markings (in the ERC-condition), which is a characteristic on which road users do not so often pay attention to. The study also gave an indication of other road/environmental characteristics on which drivers pay attention by formulating expectations. The red cycle lanes along access roads appeared to be both distinguishable (access roads) and self-explaining (vulnerable road users).
In the second study, we examined the effects of different design types (traditional design, ERC-design, ideal Sustainable Safety design) on road user behaviour (speed and lateral position). These behaviours were examined in light of general safety effects and a more specific hypothesis that underlies the predictability principle: does a recognizable road design lead to more homogenous road user behaviour (and thus to more predictable and safer behaviour)? The study showed that the road design itself has a strong effect on driving behaviour: more physical lane separation, for instance induced slower driving, and lateral position shifted towards the shoulder of the road. The study showed also an effect on more homogenous lateral positions between vehicles, but not in speed.
From both studies, we conclude that the new road design with ERC's provides a good basis for the distinction of different road types and safer road behaviour. The distinctiveness may, however, be improved further by a higher level of uniformity of road design per road type. Safer behaviour may particularly be improved by examining more carefully the specific combination of road design elements of each road type. At the moment, not so many road design elements are really 'self-explaining'. Explicit information may improve this.
Association for European Transport