The effect of signalization on road accidents in Helsinki

This paper investigates the effect of signalization on road accidents in Helsinki, Finland. The results indicate that the signalization particularly increased the safety of the minor road of T-intersections. However, the study also implies that traffic signals are not necessarily suitable for all types of intersections. For example, the safety effect of public transport signalization varied in different environments. The deactivation of traffic signals during night time was found to increase the road accidents. Accident rates were higher in general in signalized intersections compared to unsignalized intersections. The accident rate decreased along with the increase of the traffic volume, but the accident rate of signalized intersections increased again when the daily traffic count exceeded 50,000 vehicles. The accident rate also increased when the amount of phases of the signal operation increased. This implies that red light offences increase when the intersection capacity decreases. Rear-end collision is the most common accident type in signalized intersections. A comparison to previous studies shows that the proportion of rear-end collisions at signalized intersections has not decreased since 1985. This result indicates that vehicle-actuated traffic control has not solved the problem of rear-end collisions.