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Traffic Signals


Traffic signals don't always prevent crashes. In fact, in many cases the number of crashes and injuries increase after signals are installed.


Unnecessary signals can reduce right-angle collisions, but they can cause an increase in total crashes, especially rear-end collisions. In addition, pedestrians are often lulled into a false sense of security.


In deciding whether a traffic signal will be an asset or a liability, traffic engineers use the following criteria:


  • Does the number of vehicles on intersecting streets create confusion or congestion?
  • Is traffic on the main street so heavy that drivers on the side street try to cross when it is unsafe?
  • Does the number of pedestrians attempting to cross a busy main street create confusion, congestion or hazardous conditions?
  • Does the number of school children crossing a street require special controls for their protection? If so, is a traffic signal the best solution?
  • Will the installation of a signal allow for continuous, uniform traffic flow with a minimum number of vehicle stops?
  • Does an intersection's crash history indicate that a signal will reduce accidents?

Traffic engineers compare existing conditions with nationally accepted minimum standards established after many years of studies. Signals generally operate effectively, that is, with good public compliance, at intersections where standards have been met.


Where not met, compliance is generally reduced, resulting in additional hazards. Properly placed traffic signals improve flow and decrease crashes, while unnecessary signals can create danger and be an annoyance to pedestrians, cyclists and drivers.


Traffic signals are expensive to build, operate and maintain.  A typical traffic signal costs between $200,000 - $350,000 to construct. The annual maintenance cost for a typical signal is around $3,000.  The costs vary by the number of signal heads and mast arm lengths.

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Contact Information:

Transportation Engineering(1)
S. Allison Pkwy
Lakewood, CO 80226