Effects of Flashing Lights on Driver Speed Behaviours within School Zones

A trial was conducted to assess the effects of flashing lights on driver speed behaviours within school zones on a sample of 60 km/h and 70 km/h roads. Two speed surveys were undertaken on each of the selected sites within the school zones over full 5 school days of the week, four months before and twelve months after the installation of the flashing lights.

The study found that the effects of flashing lights were more pronounced during the morning than during the afternoon school zone time period. In the morning school zone time period, the flashing lights were associated with an average reduction in mean speed of 1.83 km/h, while the afternoon period showed a significantly less reduction of only 0.81 km/h. When the means were adjusted for seasonal differences in driver speed behaviours , the reductions increased to 2.62 km/h and 1.65 km/h, respectively.

The morning school zone time period showed a reduction in the 85th percentile of 2.4 km/h while the afternoon period showed a reduction of 0.6 km/h. After adjustment for the seasonal differences , it was estimated that the reduction in the 85th percentiles could be as high as 2.8 km/h for the morning and 1.1 km/h for the afternoon period.

It was found that with the installation of the flashing lights driver compliance to the speed of 50 km/h, 10 km/h above the speed limit, increased such that there was a substantial reduction in the percentage of vehicles travelling above the speed when compared to the driver compliance prior to the installation of the lights; that is, 24.3% and 12.4% for the morning and afternoon school zone time periods, respectively.

Analysis of the effects of the flashing lights by 15-minute intervals suggests that the greatest reductions in the mean speed after the installation of traffic lights were associated with the greatest mean speeds prior to the installation.

Despite the differences in the effects between the school zone time periods and within the periods, the study results suggest that the flashing lights make positive influences on driver speed behaviours when travelling through the school zones.