DRIVING SPEEDS IN POPULATION CENTERS. A SUMMARY REPORT.

A comprehensive study on driving speeds in population centers was conducted in 2000 - 2002. The impact of reduced speed limits, measures that uphold speed limits and various structural measures on driving speeds was examined on the basis of before-and-after studies. The study also gathered basic data on vehicle driving speeds in population centers. The study included nine population centers in different parts of Finland. In each population center speeds were measured at 12 measurement points over a period of two or three years. The measurements were conducted using a HI-STAR traffic counting device affixed to the road. Average driving speeds varied by population center between 45 and 49 km/h. The nature of the route and the traffic environment, road arrangements and the amount of through traffic appear to have a major effect on driving speeds. The through traffic routes of smaller population centers in particular need road solutions that reduce speeds. The speeds of heavy traffic in population centers are usually higher than the speeds of light motor vehicle traffic. The high speeds of articulated vehicles in some places are especially alarming. They may be as much as 4 to 6 km/h higher than the speeds of light motor vehicles. Driving speeds are lowest during daytime traffic. Speeds in the afternoon and evening are 1 km/h higher on average. Speeds in morning traffic are nearly 2 km/h higher than during the day. At night speeds are clearly higher than at other times of the day, averaging nearly 6 km/h higher than in the daytime. There are no big differences in driving speeds on different weekdays. Simply using traffic signs to change a 50 km/h population center speed limit to a 40 km/h area speed limit lowers the average speed of traffic relatively little, only 1 to 3.5 km/h on average, depending on the population center. Average speeds in 40 km/h speed limit areas remain quite high, around 45 to 50 km/h. The effect on high speeds is slightly greater than the effect on average speeds. 85th percentile speeds dropped 2 to 4 km/h, but depending on the population center, they are still 50 to 59 km/h in 40 km/h speed limit areas. The change in driving speeds is greatest immediately after the speed limit is lowered, but over time speeds increase a little. Speed limits and stripes painted in the lane of traffic were also used to enhance the perceptivity of speed limits. The results indicated that markings slightly lowered speed limits, and repeating the markings expanded the effect in the population center. The impact of markings on average speeds was estimated to be less than 1 km/h. An improvement project comprising Korpilahdentie, the main street of the population center in Korpilahti, was carried out in the summer of 2000. The road was narrowed, pedestrian and bicycle paths were constructed, center islands were constructed at crosswalks and intersections, lighting was renewed and roadside greenery was planted. The population center had a 40 km/h area speed limit before the study and the road project. Bumps or raised sections of road were not used to slow traffic in Korpilahti. As a result of the renewal of the population center road, the average speed of vehicles on Korpilahdentie dropped 2 km/h and the 85th percentile speed dropped about 3 km/h. The share of vehicles driving over 60 km/h was quite small already before the measures (5.6 %), and it decreased to 2.5 % after the measures. The share of vehicles exceeding 50 km/h and 40 km/h was reduced by 7 to 8 %. Two years after the measures were implemented the speeds remained the same, meaning the impact was permanent. By using structural measures and a 40 km/h area speed limit, speeds on Korpilahdentie were reduced to a level that is lower than in most of the population centers under study. The nature of the route, which is a business street with no through traffic, also contributes to the low speeds.