Street lighting and road safety on motorways.

It is now broadly accepted that street lighting indeed assists in reducing the number of night-time accidents and that the associated level of luminance of street lighting plays a role. However, these assumptions still need to be confirmed through a specific relationship study. This report relates to the study of the cited relationship with respect to motorways outside the built up area. The principal policy queries to which this series of studies is intended to offer a reply are as follows: Under which conditions and on which roads is the installation of street lighting useful, above which level of luminance is no further improvement in road safety likely and what is the most effective level of luminance ? The data for approximately 2000 kilometres of Dutch motorway was reviewed. The collected data and results respectively were entered into a research matrix, composed on the one hand of a number of traffic intensity categories and on the other of a number of luminance categories. Per matrix cell, the night and day risks, as well as the night/day risk ratios were calculated for both lit and unlit road sections. A conclusion that can be made is that most trends point towards the positive effect of street lighting. However, the nature and scope of the available data do not allow a reliable and accurate quantitative relationship to be established between the level of street lighting and road safety. (A) Also published as: Leidschendam, SWOV Institute for Road Safety Research, 1994, 22 p., 13 ref.; D-94-18, see C 21579