The City of Madison is changing how the signal timing operates through most of the City. In the past, each signal was timed to handle the traffic flowing through it as a separate signal, independent from all other signals. Up to four different timings were set in each signal to accommodate the traffic demand at different times of the day. Traffic flow through each signal may move with relative efficiency but traffic could theoretically be stopped at each signal because they act as individual, unconnected signals.
We have begun to coordinate the signal timing to improve traffic flow along our primary routes. The signals are programmed to start the green cycle in sequence that will improve the continuous flow of traffic along the primary route. Unused side street or left turn time is added to the green light in the primary direction of travel and that green time will run full cycle regardless of gaps in traffic that would trigger a signal change in the old system. The green light is maintained to allow the passage of platoons of traffic being released from adjacent signals on the primary routes. We have completed the signals on Countyline Road and are working on the signals on Hughes Road and Sullivan/Wall Triana. We are monitoring the signals and making adjustments as appropriate.
We have several intersections in the City where the left turn arrow for the side streets come on after the green light. The use of the lagging left saved time as independent signals but provide no benefit for coordinated signals. All lagging left turns in the City will be phased out as the coordinated timing is implemented. Be aware of the changes and follow the new signal phasing.
Gary L. Chynoweth PE
Director of Engineering
City of Madison, Alabama