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Report numberRA-2006-97
TitleEffectiveness of traffic measures: speed reduction from 90 km/h to 70 km/h on regional roads
SubtitleResults from Flanders
AuthorsFrank Van Geirt
Erik Nuyts
Published byPolicy Research Centre for Traffic Safety 2002-2006
Number of pages34
Date13/10/2006
ISBN
Document languageDutch
Partner(s)PHL
Work packageOther: Infrastructure and space
Summary

In this study, the effect is calculated of a speed limit change from 90 to 70 km/h on Flemish roads. The accident data is gathered within the police regions. The effects are calculated with the software CESaM. The study is made for all accidents and only injury accidents.
 

When the dispersion factor based on the accidents of the comparison group is used, no effect can be calculated since the dispersion factor is negative. In second instance analyses are made with fixed dispersion factors, varying from 0 to infinity. In all calculations, we find half of the roads with an increase and half of the roads with a decrease of the number of accidents.
 

In the most probable situation (dispersion factor = 0,37) we find not significant increases of the number of accidents by 6% (all accidents) and 8% (only injury).
 

When the comparison group is less important in the calculations (dispersion factor = ¥), we find not significant effects of 0,90 (all accidents) and 0,96 (only injury). So, a small decrease of the number of accidents, but statistically not significant.
 

The only significant meta-analysis is found for all accidents with the usage of a dispersion factor = 0. In that case we find an increase in the number of accidents by 47%, which is statistically significant. A dispersion factor = 0 actually means that the research location is less important in the calculations, so this situation is highly implausible.
 

When we do not use a comparison group, and thus make no correction for regression to the mean and the trend, we find not significant increases of the number of accidents of 26% (all accidents) and 19% (only injury).
 

Based on the available data for this study we do not find a common trend for the effect of a speed limit change from 90 to 70 km/h on Flemish roads. Further research is appropriate.

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The Policy Research Centre for Traffic Safety carries out policy relevant scientific research under the authority of the Flemish Government. The Centre is the result of a

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