Not even just lefts; in SF now most[0] lights will show a pedestrian walk sign around 5 seconds before any light in that direction switches from red to green. So pedestrians will have a chance to make themselves seen before cars do anything.

It's also useful if you're a pedestrian going in the perpendicular direction. If your light turns yellow, you still have another 10 seconds to get across (5 seconds for the yellow->red transition, and then another 5 seconds before the opposing light turns green). Granted, this isn't universal (see below), so you still need to pay attention and sometimes hustle across.

[0] Weird that it's not all, but I still see many that turn simultaneously still.

Lefts in drive_on_right jurisdictions are privileged because they cross lanes of traffic. Privileged means they have to have priority on signal change - start and stop. In driver's Ed, it is taught that the first queued vehicle making a left turn can take it even though a light may have just turned to red when the opposing traffic has stopped. Similarly, a left turn signal is activated before the through signal to allow any queued left to turn and provide a gap to the traffic behind it to turn to any right lane if additional cars become queued in front unable to make the left turn. Further, drivers cannot be expected to keep track of and attempt to predict the movements of a crowd of people, only avoid hitting obstacles in their direction of motion. If any pedestrian cannot get across in 5 seconds, then a change to green on the parallel vehicle traffic lane could be mistaken as absolution from liability. The point is to reduce confusion. At crosswalks, pedestrians really only have one rule: Don't run out in front of a car, making it impossible for the driver to stop in time. Any start "delay" along with accelerated stop should occur on the pedestrian signal as people do not move in single file "lanes", but rather as a group that is able to handle a decreased queue elimination time with the expectation that the duration of the parallel through green is long enough for all queued pedestrians to cross.

> Privileged means they have to have priority on signal change - start and stop

Citation needed. Traffic laws vary widely based on the jurisdiction.

> If any pedestrian cannot get across in 5 seconds, then a change to green on the parallel vehicle traffic lane could be mistaken as absolution from liability.

No, if you hit a pedestrian in the crosswalk and they have the green, the driver would be at fault in a jurisdiction like NYC.

In Norway, you Are never allowed to enter the intersection on a red light. If you want to turn left, you move into the intersection when the light turns green, then stop if needed. At that point the light doesn’t matter to you anymore, and you proceed once the way is clear. With heavy traffic in the opposite direction, that often means after the light turns red.

Thats pretty much the same situation as over here, in Austria. Police is perfectly fine if you drive out of an intersection when it is red. But driving into it when it is red, can incur a HEFTY fine.

Also: A arrow on the signal means you can just go, a full blob means you have to be careful about other traffic.

So we have a few intersections where left turns are on a different timer, where ONLY the left turning traffic goes. Usually before the head on traffic gets green. Or where the arrow extends it for the left turning traffic, so they still are allowed to drive into the intersection when straight on wouldn't.

I think you and the person above you are talking about the same thing.

They're different things.

the parent comment is describing a scenario in which

straight (including pedestrians have green) -> straight gets red -> left gets green.

in NYC's LPIs, this is

all directions have red -> pedestrians get green -> straight + left get green with pedestrians