Delayed actuation at a right-turn-on-red (RTOR) location allows a driver to turn right onto the cross street without requiring green time. This increases the efficiency of the signal and reduces delay to cross-street motorists. However, there are no analytically based guidelines to assist the traffic engineer in selecting the appropriate length of delay for RTOR applications. A questionnaire sent to city transportation departments indicated that 100 percent based the length of RTOR delay on engineering judgment, field observation, or both. An analytical process used to determine the appropriate values of RTOR delay is described. Equations of motion and statistical relationships are applied to the three maneuvers of an RTOR. The calculations indicate that RTOR delay settings are primarily dependent on the loop length and the traffic volume in the outside lane of the cross street. The speed of crossstreet traffic also impacts the length of delay but to a lesser extent than loop length or traffic volume. The resulting guidelines for RTOR settings are based on total loop length, traffic volume in the outside lane of the cross street, and speed of the cross-street traffic. The guidelines indicate that 7 to 10 sec is appropriate for locations with low cross-street traffic volumes and 9 to 13 sec, for locations with higher cross-street traffic volumes. The higher delay values in these ranges should be used for longer loop lengths and higher cross-street speeds.

The first traffic-actuated signal was installed in Baltimore in February 1928; it used a sound box as the detector (I). A driver sounded the vehicle's horn to obtain a green indication. Fortunately for those living near signalized intersections, detector technology has advanced considerably in the intervening years. Today, traffic engineers use the many advantages offered by actuated signals to improve traffic operations at signalized intersections.