Hur förändras trafiksignaler i drift ? : effekter av driftstid i olika trafikmiljöer : slutrapport = How does the performance of traffic light signals change ? : longe-term performance in different traffic environments : final report.

Ten traffic light signals of three different makes (i.e. 30 signals) were studied with respect to changes after five years of exposure to "hard" and "soft" traffic environments in Gothenburg. For each of the 30 signals, the red, yellow and green colours of the signals were determined and the light distribution of the red signal was measured when the signals were new. These measurements, carried out in a laboratory, were then repeated after five years of exposure in traffic. The results of these two series of measurement were then compared. Furthermore, each Spring a simple relative "measurement of light level" was carried out on each traffic signal in the traffic environment. The signals was first measured with a dirty lens and then when the lens had been cleaned manually. (A).