There are plenty of intersections where a walk signal comes on automatically, why do some intersections require a button push to initiate the walk signal when it doesn’t seem to make a difference in light timing or duration?
In: Engineering
It depends on location, in areas with high traffic, the button does actually trigger a shorter timeout to force the lights to change. This is the case here in the San Jose metro area. I have heard that similar buttons in SF do nothing to affect timing, but instead they produce audible feedback for the visually impaired to let them know whether it is safe to cross.
In some cases, the traffic control cycle is suitable for pedestrian crossing. This works well at intersections where the cycle is timer based. The light just changes in a rotation. But there are other cases where this doesn’t work so well.
For example, some signal lights will only cycle when a vehicle is detected at the intersection. In this case, a pedestrian would have to wait for a car to arrive, which isn’t desirable.
Another cases is where the standard cycle isn’t safe for pedestrians. Fore example large intersections with dedicated left/right turn lanes and various dedicated signals are especially dangerous for pedestrians. The issue is that vehicles do not have adequate line of sight to clear the destination lane of pedestrians prior to entering the intersection. If a vehicle starts to go, only to see a pedestrian in the way, they would be forced to stop in a place that would be dangerous for everyone. Or they may panic and drive around the pedestrians in a way that is unsafe.
In these circumstances, the traffic control cycle will be altered to improve safety for pedestrian crossing. This can be implemented as a red signal in all directions, a delayed green for particular lanes of travel, or even a skip cycle where certain lanes of travel don’t get a green at all for that cycle.
Different uses for different intersections. The ones where the walk signs come on automatically are generally unmanaged as far as pedestrians go. For reasons regarding the type of vehicle and foot traffic at that intersection, it’s best to just run the normal cycle every time.
For others, you’ll want to change the cycle based on how many cars are in which lanes, or if pedestrians are wanting to cross. For that they have magnetic sensors in the road to track the cars, and the buttons for the pedestrians.
In an extreme example of this, there’s on intersection in my town where the light is always green for north/south traffic unless a pedestrian hits the button.
Two traffic lights by me operate differently. One unless you push the button or a vehicle is in the detection loop it does not change at all. There is a X walk count down timer for the main road and the timer counts down to 0 and then goes back to cross.
The other one the lights change from green to red on the Main Street but the crossing does not give a walk signal to cross unless you hit the button. It is also a shorter time for vehicles to turn from the side street.
I’ve seen intersections where the pedestrian crossing button delays turn signals. If the button is not pushed, the crossing signal stays red, and the turn lane gets to go right away.
Push the button and the turn lanes have to wait for the pedestrian crossing signal to end.
The ones with the button have vehicle-activated lighting.
There’s an inductive loop in the street, that a computer system uses to sense how busy each side of the intersection is (Sometimes each lane of each side) by sensing when cars are stopped on top of it.
Since this sensing system doesn’t account for pedestrians (sometimes it struggles with motorcycles – not enough steel in the frame), there has to be a way to tell the computer that pedestrians are waiting.
Ergo, the push-to-walk button.
It should make a difference. Where I live, at the intersections where I’ve paid attention, the green signal is noticeably longer if the pedestrian button is pushed than if not. There are standards for pedestrian crossing times, and it’s usually set to accommodate the slowest possible pedestrian. If no pedestrian had pressed the button, car-centric planning dictates that the cycle should be set to whatever moves cars through the intersection as fast as possible.
Where the ped signal comes on automatically, there’s two possible reasons: 1) pedestrians are so common there that they might as well always leave it on. 2) The light cycle when optimized for cars already allows enough crossing time, so the button would be an unnecessary step.
The button might be there for one of several reasons:
* It might turn on a voice/sound indicator for crossing.
* It might make the pedestrian light come on sooner than automatically scheduled.
* It might control the crosswalk only during certain times of the day/night.
* It might be left over from a time when the crosswalk used to be pedestrian-controlled.
It can 100% make a difference in areas where pedestrians traffic fluctuates heavily, or is rare.
With the button you can alter the timing of the lights based on demand.
For example if you have a busy arterial road and then a not busy side road, stopping the arterial road every minute for a side road/cross walk that might not even have anyone standing there is a waste of time.
Better to only stop when it’s actually needed
It does make a difference, it give more time to cross. The pedestrian lights will still change when the traffic allows but they won’t get the increased time, often times I have to run before the light changes. This keeps from holding up traffic lights when there’s no pedestrians there
Latest Answers