The effect of Your Speed Signs on speed and road security

Student thesis: Master thesis (including HD thesis)

  • Mads Skov Thomsen
Since the beginning of the nineties the Your Speed Signs have been used in Denmark as means of reducing the speed level on road stretches. The measure is mostly implemented in connection with city entrances in the transition zone between rural and urban areas. Through time several evaluation studies of Your Speed Signs effect on the level of speed have been performed. However the same is not the case for the effects on traffic safety.
Generally USA is the country in the world, which has contributed with most experience within this area. Since the experience hardly can be transferred directly into Danish practice, it was decided to carry out a more detailed study on Danish Your Speed Signs, analyzing the effects on both speed and accidents. In that connection there has been made an evaluation of Your Speed Signs, in which both speed and traffic safety are evaluated. Statistical tests have been applied to prove, if the effects are significant on a five percent level of significance. In the analysis of speed the focus has been to prove respectively, if there will be a significant displacement of speed levels from the before- to the after period and, if Your Speed Signs leads to a significant reduction in the share of speeding violations. The results of the analysis of speed show that a significant displacement of speed levels arises from the implementation, and similar a significant reduction is seen in the share of speed violations. On average, the results show a reduction of 40 percent in the share of speed violations.
To evaluate the effects upon traffic safety it has been tested, if the number of accidents respectively the number of accidents with personal injury is significantly reduced from before to after the implementation of Your Speed Signs. The results of the analysis on acci-dents show an increase in the number of accidents, but a reduction in the number of accidents with personal injuries. However, the small number of analyzed locations and the very small number of accidents makes it impossible to identify significant effects on the number of accidents both generally and in terms of accidents with personal injury.
A more detailed investigation of the accidents in the before- and after period concludes, that the results is highly under the influence of random variation in the accidental occurrences. As an example, a large number of parking related accidents have happened in the after-situation, where none of this type occured in the before-situation. Such an increase may be under influence of random variation in the accidental occurrences. The guiding value of the results of the analysis of accidents seems thereby to be quite small. It will simply require much more road stretches in the analysis to get a significant result.
To deduce more from data, it will be an advantage, if speed data is measured for each vehicle and not aggregated in speed intervals. Equivalent to this, it is necessary to use a much larger number of road stretches in the analysis of accidents to get significant results in the associate statistical analyses.
LanguageDanish
Publication date16 Jun 2011
Number of pages142
Publishing institutionAalborg Universitet
ID: 53001736