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 makes a big difference in the light timing. The length of time a ped signal is up is based on the length of the crosswalk, usually 3.5 feet per second. Depending on the width of the road, the crossing time could be anywhere from 15 seconds to 60 seconds or more. And the traffic lights will be green this whole time.
The time a light is green is usually based on the traffic, especially for the small side streets. The light will only come up if the intersection detects a car waiting, and it should only stay green long enough to clear out the line of cars. If there’s only one car waiting, it’ll be green for a minimum time of about 8 seconds, then go yellow and red. The idea is to get back to the main road being green as soon as possible, since that’s where all the traffic is. However, if someone pushes the ped button, now it’s gonna be stuck in green for 20, 30, 60 seconds, even if there’s only 1 or 2 cars. It’s a giant waste of green time, at least from the point of view of the motorists. So the press of a button is the difference between an 8 second green and a 40 second green, along with an equivalent red time for everyone else.
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