Overtaking lanes were built on two steep climbs on a main road between Tampere and Hameenkyro in 1984 in Finland. The road and traffic laboratory investigated the lanes' effects on traffic flow as a before and after study. The overtaking lanes naturally caused an increase in the number of overtakings on the climbs, where the lanes had been built. The effect of the lanes on the number of overtakings increased with the density of the traffic flow. Owing to the increase in the number of overtakings, travel speeds on the climbs increased with 3-9 kmph for different traffic volumes while the percentage of vehicles driving in platoons decreased by 7-13 units. The effects of the overtaking lane also extend to the road section following the lane where it was found that travel speeds increased by 2 kmph on the road section after the overtaking lane, in spite of the increased traffic volumes. The effects were, however, quite restricted. At the measurement point situated about 5 kilometres after the end of the overtaking lane, the percentage of vehicles driving in platoons was about the same as before the overtaking lane.
Abstract