Traffic Controllers & Timing Strategies
Traffic signal cabinets house the equipment that operate a traffic signal including the traffic signal controller which is responsible for processing detection to activate vehicle, bicycle, and pedestrian indications. Traffic signal controllers operate on two primate hardware platforms, Type 2070 and NEMA platforms. Think of these traffic signal platforms like PC or Apple computer hardware, respectively. Both platforms offer equivalent operations benefits and new traffic signal detection solutions introduced into the marketplace must operate in both hardware environments.
The traffic signal controller will determine the level of bicycle- or pedestrian-specific timing features that can be implemented at an intersection. The simplicity in which features can be implemented will vary by manufacturer. The detection equipment differentials vehicles from bicycles and pedestrian and provides this data to the traffic signal controller through “detection channels”. A modern traffic signal controller allows users to define the type of detection channel input provided so that unique signal timing strategies can be implemented. Once the detection channels are defined, the traffic
count data can be used to provide reports through a Central System, or Advanced Traffic Management System (ATMS).
The first step towards using an ATMS to store and query traffic count data is to establish a Detection Channel Strategy, preferably one that can be consistently deployed across a local agency’s network. The strategy identifies the channel input assignments used for vehicles versus bicycles. Providing a consistent detection input strategy also benefits in helping to simplify how traffic signal data can be shared with growing connected and autonomous vehicle systems through Data Broadcasting solutions.
The traffic signal controller uses the detection input on bicycle-specific channels to implement timing strategies such as:
Alternative Minimum Green Release
Traffic signals provide a Minimum Green (such as 5- to 10-seconds) for a
movement when serving a vehicle. Without bicycle differentiating detection
equipment, a traffic signal controllers services bicycles the same way it service
vehicle using vehicle specific timing features. With bicycle-specific detection
equipment providing input to the traffic signal controller, the controller can use an longer minimum green to help cyclists move through an intersection only when the bicyclist is detected.
Green Extension
If a cyclist is detected approaching the intersection as the Maximum Green for a movement is being reached, the controller can provide an Extension of Green to help cyclists move through an intersection.
Bicycle Detection Indicator
When a cyclist reaches the limit line of an intersection, the controller can use
its“special function output” feature to turn on other field devices such as an
indicator to acknowledge detection to the cyclists or to warning signs to advise
motorists of bicycles position ahead on the roadway. There is no current national bicycle indicator standard indicator but regardless of what the future standard is, it will require bicycle differentiating technology, couple with the special function outputs of the traffic signal controller to activate it.
Minimum Bicycle Timing
To ensure a bicyclists can safely move through an intersection Minimum Bicycle Timing can be provided equivalent to the sum of Min. Green + Yellow + All Red for vehicles. Below is the Minimum Bicycle Timing recommended in California by the California Department of Transportation (Caltrans). Check with your own local or state agency to determine recommended Minimum Bicycle Timing in your region.
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