[gkop]

The yellow light should be long enough for both one last car in the through direction, and one left turner. At least, that’s common outside of SF. I see your point in SF. Anyone care to comment on this? Could it be a combination of short yellows, relatively wide lanes, and nonexistent enforcement (and therefore diminished fear of all parties crossing a red light)?

[dheera]

In SF usually at the yellow light there are about 5 cars that blast through in the opposite direction at 2X the speed limit. The safest time to actually make the left turn is after it turns red, and you're, um, blocking the intersection.

Protected left turn signals are the correct solution to all of this IMO, and that's the norm in almost all of South Bay.

[gkop]

Thanks! Why are you so confident on protected lefts? Wouldn't we lose significant throughput? Why not just ticket people for running reds?

[dheera]

Most protected lefts have sensors so they don't go through that phase if nobody is waiting for it. The sensors are another issue because they don't trigger for bikes and ebikes, but that can be improved.

I think throughput isn't really a huge issue as long as you have a few main arteries (e.g. expressways, freeways) that don't have left turns at all, you will ideally only take the local roads for a couple km at the beginning and end of a trip at most.