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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 150 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 computer to help traffic move efficiently.

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, visit Inquire Boulder or call 303-441-3266.

Updates to Traffic Signal Practices

We are currently updating the city's traffic signal practices to advance the city's Vision Zero goal. To learn more, please read the draft manual pdf and section updates using the links on the right-hand side of the screen (or at the bottom of your screen if you're using a mobile device). 


We continually work to improve the existing traffic signal system. This includes:

  • updating signal timing as traffic changes;
  • changing how the signal operates by time of day to adjust for fluctuating traffic;
  • installing automated monitoring so problems can be identified and corrected more quickly;
  • automating traffic data collection to better inform changes to the system; and
  • carefully selecting new signal locations.

Upcoming Projects

For up-to-date construction impact information, please visit Cone Zones

Flashing Yellow Arrows for Left Turns

Flashing yellow arrows are the new national standard for left-turn signals where vehicles may turn when there is a break in oncoming traffic and in the crosswalk (called "permitted left turns").

Previously, drivers would see a green circle to indicate that they could turn left when safe to do so. These two signals mean the same thing, but national research has found that the flashing yellow arrow better indicates to drivers that they must wait for a break in traffic to proceed.

Where permitted left turns are allowed, we're installing flashing yellow arrows when new signals are installed and when existing signals are being reconstructed.

Flashing yellow arrows:

  • provide more opportunities for drivers to safely turn left;
  • enable the left-turn control to be varied during the day;
  • can also be used for right turns;
  • can be used in all intersections 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 lines at red lights. Many intersections have vehicle detectors behind the stop line that 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 at 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.