There are multiple causes of delay at a signalized intersection. These are summarized below.
Vehicle and or Pedestrian Detection Failure: Detection failure can be the result of a malfunction or the result of the detection device not being properly aligned to detect traffic accurately. Detection failure will cause vehicles or pedestrians to not be detected and or relay to the traffic signal controller about demands that do not exist.
Traffic Signal Preemption and Priority: Traffic signals may be designed and operated to respond to certain vehicles such as buses, trains, and emergency vehicles so that if these vehicles approach the intersection the signal phasing changes to favor that vehicle.
Preemption control in Palm Beach County is given to trains and emergency vehicles so that when they approach an intersection they may immediately and safety pass through. When a train approaches an intersection, the conflicting movements will transition to the red indication no matter where the intersection is in its phase sequence. This will also take place when an emergency vehicle approaches an intersection; however, depending on the emergency vehicle's route, a softer preemption may take place "Priority".
Start up Lost Time: A fundamental characteristic of a signalized intersection is the periodic stopping and restarting of traffic. Each traffic signal phase has start up lost time that is attributed to the driver's reaction to the change from a red to green and the time it takes for the vehicles at the approach to begin moving. This lost time adds up when a location has multiple phases, such as left turn phases.
Suboptimal Traffic Signal Timing Plans: Traffic demands change hourly, daily and seasonally. New developments such as stores, gas stations, schools, and neighborhoods also create new demands and traffic patterns in the transportation system. Traffic engineers regularly review the signal timing plans for improvements to meet these changing demands but rely a lot on citizens to alert them of changes in demand that may be causing added delays that signal timing adjustments could help alleviate. However, once an intersection reaches capacity signal retiming for delay reduction becomes impossible. There is simply not enough green time to meet the demands of all approaches. Solutions such as road widening, mass transit and other multimodal improvements should be considered as a solution to the increased demands.
The County in coordination with the Department of Transportation is implementing adaptive signal control strategies at major arterials to improve traffic flow by adjusting signal timing based on actual traffic demand. The County is also implementing new technologies to improve safety and operations using intelligent transportation systems (ITS) as well as exploring new opportunities provided by the evolving field of advanced communications between vehicles and the roadway infrastructure (signal controllers) that are already being implemented by a number of car manufacturers. Vehicle-vehicle and vehicle-highway communication is anticipated to be significantly enhanced with the implementation of the 5G network.