The idea is that pedestrians, cars, etc. get a headstart so that by the time the left is legal, any people or vehicles crossing will squarely be in the middle instead of to the side where they could be blocked by a pillar.
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.
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.
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.
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
Regarding collisions due to people running red lights: at least when waiting to turn left chances are very good that you will see the oncoming vehicle since you're already pointed towards them.
That seems much better than being first in line at an intersection when the light turns green; in that case anyone running the light may well be coming from the side. I lived in Dallas for a few years and after a few near misses I learned to always look before proceeding after the light turns green.
Of course most drivers might do this for a week after getting their license then ignore it. Like a lot of good rules.
That's only true if there are no oncoming cars lined up to turn left in front of you. Even just one car waiting can obscure an oncoming car coming around them to run the light and crash into you as you turn.