This is a call for volunteers to help measure and monitor the yellow light durations in Seattle.
I have set up a data entry form here:
The location of traffic cameras in your area of Seattle can be found here.
The results you submit will be posted here:
I measured the yellow light durations at the two intersections in West Seattle that have ticket cameras. Here are the results:
|
Intersection |
Yellow Light |
Speed Limit |
|
35th and Avalon |
3.5 sec |
35 MPH |
|
35th and Thistle |
3.5 sec |
35 MPH |
The above times are consistent with what has been stated by Wayne Wentz, Seattle’s traffic management director. Seattle PI quoted him as saying that yellow signal times were shortened as part of a re-timing of downtown signals in March 2008, to make sure intersections are cleared of vehicles when lights change.
“Many of our downtown signals were operating with four seconds of yellow time, then going directly to green for the other direction,” Wentz said. “During our recent optimization, we changed the signals to 3.5 seconds of yellow time and added one second of red in all directions for a total of 4.5 seconds. This actually increased the vehicle clearance time by 0.5 seconds.”
The “all red” time at the two intersections I observed was about one second. So that is also consistent with Mr. Wentz’s statement.
The 3.5 seconds of yellow is too short in my view for 35 MPH streets, and it is shorter than the 4 seconds recommended by others. If borrowing a second or so from the green light would screw up the city’s carefully optimized system, I would support moving .5 seconds from the all red period to the yellow light, at least on an experimental basis to gather data. That would give drivers more time to make the stop-or-go decision, and still leave a half second of all red to allow the intersection to clear.