The safety and efficiency characteristics of the road network in developed countries depend largely on the operation of the intersections, particularly in the urban areas. It is here that a majority of vehicle conflicts occur, manifesting in accidents and delays. While intersection improvement or new construction are being programmed, it is imperative that appropriate decisions on intersection type, design, and control need to be made. This research explores the effect of traffic flows, cycle facilities and traffic composition of motorised and non-motorised traffic on accidents at different urban intersections governed by a 50 kph speed limit in The Netherlands. Effects of traffic flows, cycle facilities and traffic composition on accidents were studied on the basis of police-reported accidents that had occurred at the intersections from 1994 till 1998. The data was obtained from the Institute for Road Safety Research in The Netherlands (SWOV). A total of 170 three-leg, 196 four-leg intersections and 58 rondabouts were included in the study. Further, the technique of Generalised Linear Modelling (GLM) from the SPSS package was used to develop an accident prediction model for three-leg and four-leg intersections. The objective of the modelling was to develop relationships between accident frequency and explanatory variables and factors - including vehicle and bicycle flows, intersection features, geometry, signal control and cycle facilities. The effects of each parameter mentioned above were determined by comparing the observed number of accidents for different types of intersections. The methodology that was used to determine the appropriateness of different intersections in different circumstances was through the regression analysis of available data. The data analysis showed that the different intersections were appropriate in different situations in terms of safety. It showed that more control is required at intersections as flow increases. Regarding cycle traffic, bicycle facilities of segregated cycle tracks and cycle lanes did not always provide better safety for cyclists. In some cases, cycle traffic mixed with other traffic provided better safety for cyclists compared to cycle tracks and lanes. Lastly, the traffic composition of MT and NMT had a larger influence on the safety of NMT than on the MT. The accident prediction model indicated that the risk for vehicle only accidents is lower in three-leg priority intersections and accidents involving NMT is lower in three-leg uncontrolled intersections, compared to other intersections. (A)
Samenvatting