Traffic Engineering maintains and operates over 100 traffic signals within City limits. The latest computer simulation and optimization models are used to develop and implement signal timings at all of the city intersections. The data inputs to the models include traffic volumes, lane configuration, posted speed limits, crosswalk length and other physical characteristics of the roadway that impact traffic flow.
Traffic Engineers determine the need for coordinated (synchronized) traffic signals based on traffic volumes, traffic patterns, and other roadway characteristics. Signal timing varies throughout the day depending on the intersection. The direction with heavy traffic volumes will have better progression if the traffic signals are coordinated. For example, in the morning commute, westbound (toward San Francisco) or outbound progression is favored over the eastbound or inbound progression. In the Core Area, the signal timing is more challenging and the system balances traffic flow between major left and right turns, and the through traffic.
At the Traffic Engineering division, we get a lot of questions regarding the City's 100 traffic signals. We're here to answer your questions, and please start with the following set of Frequently Asked Questions.
I've been stuck at this light forever!
There are two main reasons why this might be happening:
- You're approaching a major corridor from the side street. The major street (like Ygnacio Valley Road or Treat Boulevard) has a lot of demand, and in order to provide as much time as possible to push vehicles along these routes, the signals have long cycle lengths. That means you could be waiting to get the green for upwards of 2 1/2 to 3 minutes.
- The detector isn't working. Detectors in the City are either loops in the ground (sometimes you will see a circle cut in the pavement) that can sense the presence of your vehicle OR they are video cameras that are specially used for detection only (these cameras do not record any footage, they just see a vehicle and tell the traffic signal to change when it's ready). If you think a detector might not be working, please let us know by contacting us via the link in the sidebar.
Does pushing the pedestrian push button multiple times make it change quicker?
No. You only have to tell the traffic signal once that you want to cross. The signal will give you the green as soon as it can, after serving the remaining movements in the sequence.
Can I change a light to green by flashing my headlights?
No. Preemption is triggered by a special light mounted on emergency vehicles that flashes at a specific rate.
How do I drive through a signalized intersection if the traffic signal isn't operational?
According to the California Vehicle Code, when a signalized intersection is out due to a loss of power, all motorists must treat the intersection as an all-way stop. Please do drive with caution and stay alert!