Investigating the Capacity Reduction at Signalized Intersections with Red Light Camera along Urban Arterials

The presence of a red light camera at signalized intersections can contribute to drivers' behavioral changes. One particular behavioral change may be attributed to the fear of a possible red light running situation. This situation while may improve safety, may result in ineffective use of yellow time interval. This may affect the capacity of the intersection since less vehicles may be serviced in a given signal cycle resulting in increased queuing and congestion. Field observations have shown that drivers tend to stop at red light camera monitored intersections during yellow even in cases where there is enough clearing distance before the onset of the red signal. In this paper we improve upon our previous research in modeling driver behavior at red light camera equipped signalized intersections by using field data along signalized intersections with and without red light cameras in Baltimore. Using field data on the number of vehicles delayed at the intersections we calculate the hourly delay of vehicles from which we estimate the capacity loss at each red light camera monitored intersection along a heavily traveled arterial. The results show that the cumulative reduction in capacity due to the presence of red light camera may be quite significant, which may play a major role in contributing to the peak hour congestion in urban areas. The trade-off between safety and congestion consequences of RLCs can be investigated in future works.