Lowering the speed limit to 30 km/h in school zones: effects on speed : analysis of data of 11 school zones in Flanders. The safety of school children in traffic in Flanders is a major problem. The majority of accidents involving children take place when school starts or ends. In order to make the close vicinity of schools safer, in 2004 the Belgian government decided to lower the speed limit in every school zone to 30 km/h. This can be done with permanent signs, or with variable message signs only operating at school starting and ending hours. The aim of this measure is to lower the speed of passing cars, supposedly lowering the number of accidents and the severity of accidents in this area. This measure became effective on September, 1st 2005. This report describes the results of a case study that examines the changes in the speed profile at 11 school zones where this measure was taken. The type of signalisation was taken into account, as well as the surroundings of the school entrance. The effects on mean speed were calculated as well as for the whole day as for relevant moments like the start of school. This calculation was done with a comparison group where available, to correct for the general trend in traffic safety. Effects were calculated few months after the measure was taken and several months later. Changing the speed limit from 50 km/h to a permanent 30 km/h, lowered the mean speed and V85. In school zones with a low mean speed before the measure was taken, the mean speed didn't change much. A permanent 30 km/h zone at two schools on a road segment with a speed limit of 70 km/h, lowered the mean speed and the V85 in the first months, but after a few months, the mean speed in one zone was back at the same level before the measure was taken. A variable 30 km/h zone with variable message signs, indicating the lower speed limit only when school starts or ends, was installed in 2 school zones where the speed limit was 50 km/h. This measure lowered the mean speed during the day only minimally, and the change in mean speed at the start of school is even smaller. A variable 30 km/h zone on a 70 km/h road segment, resulted in a clear decrease in V85 speed at the start and the end of school hours, as well as the V85 of the whole day. It was found that the effect of the type of 30 km/h zone depends on the situation before the measure was taken. A permanent 30 km/h zone has the most effect on a 50 km/h road segment, while the biggest effect of a variable zone is found on a 70 km/h road segment. Locations where the vicinity of the school clearly indicated the function of the road showed a lower mean speed during the day as well as during the night. On locations where the function of the road wasn't visible, the mean speed at night didn't change much. Decision trees used by the road authorities during the decision of the type of 30 km/h zone in a certain school area, take into account the function of the road (residential or flow/connecting road) and the existing speed limit. However, in these decision trees, more attention could be paid to the readability of road and the school environment to indicate the function of the road. 1 to 3 months after installation of a 30 km/h zone on a 50 km/h road segment, this measure results in a significant decrease of -5,7 km/h in the daily mean speed, and a significant decrease of -5 km/h between 8AM and 9AM. These figures were corrected for the general trend in road safety by means of a comparison group. More than 4 months after installation, the daily mean speed decreased significantly by -6,8 km/h, and the mean speed between 8AM and 9AM decreased by -8,6 km/h (both results without correction for the general trend). In the school zone with a 70 km/h speed limit where a permanent 30 km/h zone was installed, the daily mean speed decreased significantly few months after installation by -20,3 km/h. The mean speed between 8AM and 9AM decreased significantly by -24,8 km/h. These figures were corrected for the general trend in traffic safety. Some months later, this effect lowered: the daily mean speed had decreased significantly by -4,3 km/h, the hourly mean speed decreased significantly between 8AM and 9AM by -3,6 km/h (both results without correction for the general trend). It is found that the effect of a 30 km/h zone depends on the type of zone (permanent or variable), the initial situation and the surroundings of the school. The speed limit outside the school zone and the environment give the driver information about the function of the road, and thus influences the speed behaviour of the driver. This has to be kept in mind when deciding which type of school zone should be installed. A permanent 30 km/h zone suggests a residential function, so the environment should reflect this function in order to maximise the effect of the installed 30 km/u zone. A variable zone rather suggests a flow or a connecting function, resulting in a smaller effect when installed in a residential area. When the desired function of the road is not reflected by the current infrastructure and the organisation of the environment, the effect of the installed 30 km/h zone will be small. When installing a 30 km/h zone in a school area, the environment should be reconstructed to reflect the desired function where necessary. In only one school zone, the mean speed was below 30 km/h. In all other zones, the V85 as well as the mean speed were higher than the speed limit of 30 km/h on those times the limit was valid. If the government wants the actual speed near or below the speed limit of 30km/h, other and/or extra measures (like enforcement or infrastructural changes) have to be taken. To make this case study more representative for Flanders, extension of this research and follow up research is necessary. Also, the effect on the number of accidents should be studied in the future. (Author/publisher)
Samenvatting