A Danish investigation for the period 1962-66 shows that three-lane roads in rural areas for ADT below 8-10,000 are safer than corresponding two-lane roads but in contrast they are more dangerous for ADT above 8-10,000. A later Danish investigation for the period 1967-71 of roads in rural areas shows that the three-lane sections for all observed traffic volumes are safer than ordinary two-lane sections with a width of the carriageway of 6-8m. This investigation is based on considerably more accident observations on sections with ADT above 8-10,000 than the American investigations and the first Danish investigation for which reason its results may be regarded as a more reliable basis for the judgment of the risk of accidents on three-lane roads. A special Danish investigation of the effect of the restriping of three-lane roads into two-lane roads with the same width of the carriageway concludes that no significant effect of the restriping can be proved, neither as regards the number, the seriousness of the accidents nor the distribution of the accidents by type.
Abstract