During winter 1991/1992, traffic information and data regarding road conditions were collected for some permanent traffic count stations of the Swedish National Road Administration. These data were used to analyse changes in car speeds during the winter period due to winter road conditions and the hours of darkness in relation to snow free conditions and daylight. During winter 1996/1997 measurements of travel speed were made on five pairs of road sections, with different speed limits on each pair (110-90, 110-70, 90-70), over at least two daylight periods broken down into snow free conditions and winter road conditions. Pairs of sections were selected so that they had the "same" traffic and standard, but separated by a different traffic environment, e.g. major intersection or small town, and had different speed limits. Friction measurements were made at the same time. However, the effect of the speed limit on the speed distribution of car traffic is very stable between the sections; for a difference in speed limits of 20 km/h, the difference in speed is on average 6-8 km/h, with a standard deviation for the travel speed difference of vehicles that is about 8 km/h. (A) For the Swedish version of this report see C 12933 S (IRRD E202065).
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