4 ms·

In a few US cities they have what is called a 'lag left' where the left turn lane gets a green left arrow for several seconds after the straight lanes turn red.

In a few US cities they have what is called a 'lag left' where the left turn lane gets a green left arrow for several seconds after the straight lanes turn red. This has the benefit of having left turns occur when pedestrians should not be crossing the side street at the cost of some spectacular head on collisions when drivers run the red light.

kube-system 5y ago
There are some intersections like this in my city, but I've seen some drivers blow straight through the red light in the straight lanes because, presumably, they are barely paying attention but see a green light in their peripheral.
usefulcat 5y ago
I have seen that quite often (green arrow after red for straight lanes) and had assumed that was pretty common, but I don't really know for sure. 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.
- seoulmetro 5y ago
  You can fail a driving test in Australia if you don't look whilst being first at the lights on a green light cycle. Of course most drivers might do this for a week after getting their license then ignore it. Like a lot of good rules.
- kelnos 5y ago
  > 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'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.
jjtheblunt 5y ago
Arizona is like that.
bobthepanda 5y ago
NYC and a few pedestrian heavy areas have actually started doing the reverse; delayed lefts. 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.
- cptskippy 5y ago
  I think you and the person above you are talking about the same thing.
  - bobthepanda 5y ago
    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
- kelnos 5y ago
  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.
  - potiuper 5y ago
    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.

kube-system 5y ago

There are some intersections like this in my city, but I've seen some drivers blow straight through the red light in the straight lanes because, presumably, they are barely paying attention but see a green light in their peripheral.

usefulcat 5y ago

I have seen that quite often (green arrow after red for straight lanes) and had assumed that was pretty common, but I don't really know for sure. 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.

seoulmetro 5y ago
You can fail a driving test in Australia if you don't look whilst being first at the lights on a green light cycle. Of course most drivers might do this for a week after getting their license then ignore it. Like a lot of good rules.
kelnos 5y ago
> 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'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.

jjtheblunt 5y ago

Arizona is like that.

bobthepanda 5y ago

NYC and a few pedestrian heavy areas have actually started doing the reverse; delayed lefts. 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.

cptskippy 5y ago
I think you and the person above you are talking about the same thing.
- bobthepanda 5y ago
  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
kelnos 5y ago
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.
- potiuper 5y ago
  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.