How long does it take for traffic stoplights to change from red to green and back again?

Answer 1

they are on timers and sensors so there is no way to tell

Answer 2

Yes, to all of the above. What I look for when I am thinking about a particular light is a big yellow metal box on the one of the corner. If you have one of those, you are in luck -- it is the timing box for the lights. Then I also notice the cuts in the road. These are all indication of smart traffic lights. These light are engineered to keep traffic flows in mind. For instance, most traffic signals have a default cycle, depending on prior traffic studies. (I worked for traffic study folks in my youth counting cars going in different directions.) Then one day, the engineers decided that a default cycle system wouldn't work, that the traffic changed too much using too many factors. So they had to make the default the regular, light traffic one. But in heavy traffic, they needed other things. That's why some lanes have 2 sensor sections, one a lot farther back than the first. (It's used to count the number of cars waiting to turn left.) The big yellow metal box was born. Into that box go the controls for the traffic, a computer to weigh all the factors. linkage to other boxes to time the lights right for folks to go right through a series of them at the speed limit, and sensor readers, which help the computer figure out how much time it is taking for the left hand lane to turn. It's a fascinating thing ... isn't that cool?

Answer 3

Most traffic lights have electric loops under the asphalt that detects large metal objects to trigger the light. Next time you're at a light you'll probably see (if you look) that there is a big rectangle saw cut into each lane. That's where they stuff the wires in. Also if you drive a motocycle or small car with a lot of fiberglass (like a Saturn) instead of a heavy metal car, you may find that light take longer for you to be detected or they sometimes may not detect you at all until someone else pull up behind you and help trigger the light. Also, for this reason it is important to pull all the way up to the stop bar. If you stop too far back, you may be behind the loop.

Answer 4

I basically reinterating what everyone else has said. A number of the street lights here in Detroit only work in the day becuase that is when the most traffic occurs. Also, I heard it can depend on the size of you vehicle also sometimes. Usualy, the busiest lights change the most frequent while the least frequent either take foreever or just blink. the city has even been taking down some of the traffic lights due to the lack of traffic in certain areas.

Answer 5

I'm not sure if you mean (1) complete cycle : time between greens for the same direction, or (2) the split time : green time for a direction.

The complete cycle is changing depending on sensors from the road. Old signals without those black loops on the road are fixed time, and typically around 90 seconds (depending on your city). If there are very few cars, the green time will be "minimum green" and is usually 5 to 10 seconds. Heavy volumes will extend the green 2 to 3 seconds per vehicle until "maximum green", which may be as high as 35 seconds.

Answer 6

I observe the traffic lights and they operate in two modes, sensor mode and timer mode (I actually made them up). Sensor mode, the traffic lights changes from red to green instantly. Timer mode, traffic lights changes on a predetermined time like 1 or 2 minutes.

Green turns back to Red on average of 30 seconds on non-peak times.

How do I know these? I drive a lot that I noticed that so much.

Answer 7

This will depend upon how they have been calibrated.
On some busy roads the council try calibrating them with an emphasis to alleviate congestion.
I have personally had a bad experience involving a politicians canvasser running a red light and witnessed the lights being recallibrated the very next day- The engineers do as they are told.

Answer 8

It varies as to the amount of time it is set for. A highway may be half the amount of time as a side-road. Try going into a Walmart off a major road, then back out again with a left turn.

Answer 9

It depends on the intersection and the time of day.