Frequently Asked Questions

Traffic signals are usually warranted based on minimum traffic volumes during eight hours of a typical weekday. These minimum volumes, or “warrants,” vary depending on the speed of the roadway and the number of approach lanes. For a signal to be approved, it needs to meet the necessary warrants and be justified. To be considered “justified,” factors such as access and distance to nearby signals, lane geometry, and future road plans are all taken into account. If all the necessary conditions are satisfied, and funding is available, a signal may be installed.

Traffic signals may not reduce crashes at an intersection. Typically, when a traffic signal is installed at an intersection, the total number of crashes increases, but the severity decreases. Traffic signals may result in a decrease in right-angle crashes. However, they may also result in an increase in rear-end crashes.

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The length of your wait depends on the traffic signal cycle length. The traffic signal cycle length is determined based on traffic volumes and traffic patterns specific to each site. Heavily congested major corridors may require longer cycles to accommodate higher volumes of traffic. Though these longer cycle lengths may move more vehicles through an intersection in a given time frame, they may increase delays for some drivers. Typically, wait times are no longer than three minutes to get a green.

Traffic signals are timed to minimize stops and delay to all traffic using the intersection and "perfect synchronization" is rarely possible. Many factors contribute to the disruption of ideal progression: varying speeds, the presence of left-turning signals, the distance between signals, varying amounts of green time required by traffic on cross streets, and congestion from very high traffic volumes. Perfect synchronization for one direction of traffic on a street may result in frequent stops and delays for the other direction. A compromise that favors the heavier direction of flow is usually best.

Alabama Department of Transportation and City of Dothan can require that left turns be “protected” (green arrow only) when either there are dual left turn lanes, turning volumes are high, the posted speed limit is high, sight lines are restricted, there is pattern of left turning vehicle collisions, or when there is a combination of these factors. Relaxing the policy would reduce wait time at traffic signals and save fuel, but would also likely cause an increase in severe crashes.

Left turn signal phases facilitate left turning traffic and usually improve the safety of the intersection for left turning vehicles. However, this is done at the expense of the amount of green time available for through traffic and will usually reduce the capacity of the intersection. Left turn arrows also result in longer cycle lengths (if in coordination), which will in turn have a detrimental effect by increasing stops and delays.

The amount of green time for each movement at a signalized intersection varies according to vehicle demand. When there is not enough green time for each movement to get through the intersection it is often because the intersection is over capacity and has more vehicles than it was designed to handle. The city attempts to time these traffic signals to minimize overall delay for the majority of motorists at the traffic signal. Therefore, if you are on a minor approach or a side street, you may experience significant delay where the main movement is along a heavily congested corridor.

Except for a few signalized intersections that meet strict requirements, the city does not place traffic signals in flashing operation during periods of low traffic. The primary reason is for safety.

Learn about the pedestrian signals on the