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Traffic Signals Brochure

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
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