This is a case-study of the road safety effects of the redesign of the road called Kûkhernewei, in the Frisian boroughs of Dantumadeel and Tytsjerksteradiel. Special attention was paid to the effects of a narrowing of the cross section on motor vehicles’ driving speeds and on the distance between cars overtaking cyclists. In the situation before the redesign, the road was between 5.35 and 5.70 metres wide, and had no marking. Afterwards, the cross section of the Kûkhernewei had been altered considerably: the free carriageway width was reduced whereas the road surface quality and its evenness had been greatly improved. Afterwards, the road width was 4.90 metres, of which 3.50 metres was intended as carriageway, and 1.40 metres as surfaced reserve space. In the length alignment, the road was so designed that the freely useable part of the carriageway (the axis offset) regularly shifted from the left to the right hand side of the road surface. Poles were positioned at every shift. The changes made to the Kûkhernewei did not demonstrably alter the traffic intensity. The average speed decreased by 5 km/h; a positive safety effect can be expected from this. The distance between cyclists and overtaking cars was smaller, whereas, compared with roads previously studied, the overtaking distances were already relatively long. The reduction in overtaking distance can be the result of the narrowing, but also of the reduced speeds. It is not clear what the critical overtaking distance should be. Nevertheless, a relatively large increase in overtaking distance could possibly have a negative effect on the safety of cyclists. The experiences of road users living in the vicinity were measured using a postal survey. This showed that, after the alterations, cyclists found the road slightly less clear and slightly more dangerous. They also found cycling required a greater effort. In addition, they said that they had more hindrance from cars and lorries on the road. Motorists found the road especially less clear, and also had more hindrance from other cars and lorries. Some of those living in the vicinity spontaneously complained about dangerous and unclear situations for cyclists and cars. In short, it can be established that the alterations to the Kûkhernewei have not lead to any demonstrable changes in the amount of traffic on this road. Although the average speed decreased, the much shorter overtaking distances and the negative experiences of the road users do not provide a positive picture of the redesign’s safety effects.
Samenvatting