Questions about Traffic Signals? It’s Answer Day!

Earlier this month, we asked folks to submit their questions about traffic signals. Here are some questions, and our answers:

Is running a red bicycle signal a ticketable offense in Seattle?

Bicycle riders violating a traffic signal specifically labeled for bicycle users is a moving violation and is a ticketable offense, according to state law.

Why does my left turn arrow go to red, instead of flashing yellow?

In signal operations we use 3 different types of turning sequences:

  1. Protected (green arrow to yellow to red)
  2. Permissive (green circle or flashing yellow arrow)
  3. Protected/Permissive (a combination of the first two)

In other words, this question is asking why a signal may be protected instead of protected/permissive. Our signal engineers use federal standards, internal policy and industry best practices to determine how to operate a turning signal. We take into account crash history, sight lines, the number of lanes coming in the opposite direction, and the number of cars both turning and coming in the opposite direction to determine if we think the driver will likely have enough gaps to make a turn safely.

I was in an accident. Can I get camera footage to prove I wasn’t at fault?

Sorry, no. While SDOT has over 200 cameras that we use to monitor traffic conditions, we do not use them to continuously record traffic.

I can only cross one or two lanes before the “Don’t Walk” starts to flash. 

The flashing “Don’t Walk” is kind of like a yellow light. It means do not enter the intersection.  There is research on typical walk speeds and federal standards developed to give engineers an idea of how fast most people walk. The flashing “Don’t Walk” is timed with that walk speed so that most people can enter and clear the intersection before the opposite movement turns on.

Does flashing my high beams make a signal change faster?

No. In Seattle, we have some signals that are triggered by detectors and some that aren’t. SDOT does uses a few types of detectors for vehicles: inductive loops, video, and magnetometer. Flashing your lights does not help with any of these types of detectors.

And now you know! Thanks for your questions!