The majority of Douglas County traffic signals are coordinated (timed), depending on the time of day, the location, and (when applicable) the primary direction of travel. In order to maintain consistent coordination of our traffic signals, time clocks at each intersection must remain synchronized, usually by means of communications with the Traffic Management Center. Coordinating traffic signals to facilitate traffic flow in both directions simultaneously (for example, when there is no clear primary direction of travel) is much more complicated than simply facilitating traffic flow in only one direction (e.g. a one-way street). There are many factors that can affect the design of timing plans, including: volume of traffic on the side streets, crossing time required for pedestrians, distance between traffic signals, speed limit on the main street, total overall traffic volume, volumes of turning vehicles, and number of lanes available for each movement of traffic.
Most of Douglas County’s traffic signals operate on three different timing plans, which include AM Peak plan, Mondays to Fridays; PM Peak plan, Mondays to Fridays; and Off-Peak plan, Mondays to Fridays and weekends. There are also additional timing plans in some locations for special circumstances, like school traffic, weekend, heavy lunchtime traffic, or holiday shopping traffic. When traffic signals are not running in coordination, they operate in one of several different possible modes that depend on the equipment available at each particular intersection.
Additional factors – over which Traffic personnel have no control – affecting the actual effectiveness of the timing plans include: the actual speed of traffic, the acceleration patterns of motorists, variations in the volume of traffic during the timing plan, the frequency of emergency vehicle pre-emption, and the frequency of pedestrians (having pushed the button to cross) each cycle.