Effects on traffic safety : blackspot detection and remedial action in four Danish towns.

The municipal roads in Denmark accounts for more than 3/4 of all casualties. Of these, 4/5 happen in urban areas - far more than their share, despite the fact that in Denmark more than half the total traffic volume is in rural areas. This indicates a substantial accident reduction potential for a black spot treatment in local, urban roads in Denmark. Realising this, the Danish Department of Transport (Trafikministeriet) in 1985 offered 4 towns a 50% grant and planning assistance in a black spot project. Black spot detection and choice of remedies was carried out in 1986, construction in 1987, and in 1991 the effect studies began. A total of 60 black spots were eventually selected. Remedies chosen covered a broad spectre from cutting down hedges and moving road signs and markings to closing business streets and establishing big roundabouts. However, most remedies were of low cost. The total cost of all 60 rebuilds was only 6 million Kroner, equivalent to 700,000 pounds. The planning process was not entirely peaceful and straightforward. Although project acceptance was fairly quickly obtained from the politicians and the public, taxi drivers and bus drivers were hard critics, at least until the projects were completed. The subsequent statistical analysis was designed to assess the overall net safety effect from the project. This meant that two important factors had to be eliminated: namely 1) the general trend in the period considered, and 2) the bias-by-selection always encountered when performing black spot detection. This was obtained by careful treatment of all data available. The final effect was an overall reduction of 12% on all police reported accidents and a reduction of 21% on accidents with casualties. It is believed that a maximum of 30% of road accidents are influenced by the road environment. Considering this, the result of the project is interesting in having achieved a large percentage of the possible effect - and even more interesting if one considers the first year benefit, which exceeds 80%, using the Danish pricing of road accidents. (A)