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Traffic Signals

Traffic Signals

The City of Boulder's traffic system is designed to be as efficient as possible while providing safe travel for all transportation options. There are more than 140 traffic signals throughout Boulder, including mid-block pedestrian signals. All of the traffic signals are run by a central computer system and each signal has its own controller computer that is programmed for the best efficiency.

Outages and Issues

To report a traffic signal outage or other urgent safety issue, call Boulder Police dispatch at 303-441-3333.

To submit a non-maintenance traffic signal request, such as a question about traffic signal timing or locations, select the "Traffic Signal Service" link or call 303-441-3266.


The Transportation Division is continually working to improve the existing traffic signal system. This includes:

  • updating signal timing as traffic volumes and patterns change;
  • changing the signal operation by time of day as traffic conditions vary;
  • installing automated system monitoring so problems can be identified and corrected more quickly;
  • automating traffic data collection so information is available for timing plan design; and
  • carefully selecting new signal locations.

Flashing Yellow Arrows for Protected Turns

Flashing Yellow Arrow left-turn displays have been adopted by the Federal Highway Administration as a new national standard for permissive left-turn operations. The City of Boulder is installing this display when new signals are installed and when existing signals are being reconstructed.

Flashing yellow arrows:

  • eliminate the "left-turn yellow trap" and the need for a red/green arrow to avoid the trap;
  • provide more opportunities for drivers to safely turn left;
  • do not require optical shielding or precise placement – signals are placed wherever protected left-turn singals are normally placed;
  • enable the left-turn control to be varied during the day;
  • can also be used for right turns;
  • can be used in all intersection and layouts; and
  • eliminate motorist confusion as to the meaning of the circular green light (this is occasionally mistaken as a protected left turn), and the simultaneous circular red light and green arrow (some motorists stop).

Tips for Motorists

  • Drive the speed limit. Signals are timed to work best when traffic goes the speed limit. Driving faster will simply get you to the next signal too early, causing you to stop more often.
  • Stop behind stop bars at red lights. Many intersections have vehicle detectors (wire loops) embedded in the pavement, which tell the computer that you have stopped.

Tips for Bicyclists

  • Stop on the bike symbol for a green light. Bikes can activate traffic signals just as cars do. Stop your bike directly over the bike symbol on the pavement. This will position you directly over the bicycle detector.
  • Use pedestrian signals on paths. When you're riding your bike on a path and come to a traffic signal, use the pedestrian push button and follow the pedestrian signals.

Traffic Signals Videos

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