This field study was designed to compare the effects of two technologies used in variable speed limit signs on (a) speed behaviour, (b) recall of signs, and (c) recognition of variability of a sign. The speed limit signs used fibre-optic technology and electromechanical technology equipped with a fluorescent retroreflective sheeting. Data was collected in two lighting conditions, daylight and night-time. The results showed that a variable speed limit sign with fibre-optic technology is more effective than an electromechanical sign. Although the overall speed data in daylight did not support this conclusion, the interview results suggest that the relatively strong effects of the electromechanical sign were limited to drivers passing the site less than weekly. In the dark, the more substantial effects of the fibre-optic sign were evident in greater effects on speed, and in the higher recall rate of the speed limit and variability of the sign.
Abstract