How is it Determined if a Traffic Signal is Needed?

Study needed.
Unless a study has recently been completed, an agency typically will respond to a request for a traffic signal and complaints about an intersection by conducting a special traffic engineering study to obtain and analyze the pertinent information.

Important Considerations.
This study considers a number of important factors, including the following:

• Intersection design
• Accident history and potential
• Vehicle traffic volumes and gaps in traffic approaching the intersection
• Turning traffic and pedestrian crossings
• Approach speeds and sight distances
• Locations of nearby signals
• Characteristics of the area and adjacent land use
• Projected and planned growth

Digesting the facts.
With the facts in hand, engineers look to determine what actions, if any, will yield the best results with the least adverse side-effects. When considering the possibility of a traffic signal, the engineers must, by State and federal law, consider the guidelines for signal installation set forth in the national Manual on Uniform Traffic Control Devices, which embodies time-tested recommended practices developed to ensure that signals are used where, but only where, they are justified by comprehensive, objective criteria.

What are the Alternatives to a Traffic Signal?

Are there alternatives?
Where a problem is documented, experience has shown that other improvements, alone or in combination, may work better than a new traffic signal to enhance the operation of an intersection. They often can alleviate the problem without the adverse side effects that a signal may cause. Alternatives to a traffic signal can include:

• Improving the line of sight along the intersection approaches
• Installing flashing signals (beacons)
• Adding turn lanes
• Constructing curbs and pedestrian safety islands
• Revising traffic controls, measures, and regulations
• Installing/revising traffic signing and marking
• Rerouting crossing traffic to safer locations
• Retiming nearby signals
• Installing intersection lighting
• Constructing a roundabout
• Making other roadway improvements