Results
The Insurance Institute for Highway Safety recently conducted a field study to evaluate the effects on red light running by first lengthening yellow signal timing, followed by the introduction of red light cameras. Results showed that yellow timing changes reduced red light violations by an average of 36%. The addition of red light camera enforcement reduced red light violations by an additional 96% beyond levels achieved by longer yellow signal timing alone.

At the intersection with the greatest incidence of red light running - 251 incidents per 10,000 vehicles - yellow light extensions reduced red light running to 198 incidents per 10,000 vehicles. Once red light cameras were installed, incidents of red light running dropped to an astounding two per 10,000 vehicles.*

(*Source: Insurance Institute of Highway Safety Status Report, Volume 42 No. 1 January 27, 2007; Retting, Richard A.; Ferguson, Susan A.; Farmer, Charles M.; Reducing Red Light Running Through Longer Yellow Signal Timing and Red Light Camera Enforcement: Results of a Field Investigation, Insurance Institute for Highway Safety, January 2007.)