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Questions tagged [traffic-light]

Traffic lights are coloured lights that are used to control traffic flow. They instruct traffic when it must stop (usually a red light) or may proceed, or continue to proceed (usually a green light). In some countries intermediate lights (usually amber) may also be used when changing from Stop to Go or from Go to Stop.

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1 answer
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Adding traffic lights to a junction, what is the logic of using lights with arrows?

I'm doing a job and one of the feature is adding realistic traffic lights to junctions of a network and I have to be very specific. So, if on the ground there are arrows signaling the traffic flow (e....
0 votes
2 answers
376 views

What color do green traffic lights have?

A friend of mine who is (completely) red/green color blind once told me that he can distinguish the green traffic light from the yellow and red one despite his color blindness and that he thinks to be ...
0 votes
1 answer
117 views

How do "Your Speed" Signs work, and how do vehicles know when it's the sign's turn to display their speed?

I see these LED speed signs on the side of the road, which display the approaching vehicle's speed. What I have gathered is that they measure the time between the sending and receiving of the signals ...
2 votes
1 answer
86 views

Where to acquire / create LED optics

I'm working on a few projects that require lenses to focus LED light flashes, similar to those lenses used by police lights (TIR lens) and other strobe traffic lighting utilizing Fresnel lenses. I've ...
35 votes
12 answers
46k views

What are the pros and cons of a traffic circle versus a traffic light intersection?

The debate of traffic circles (also called roundabouts or rotaries) versus traffic light intersections has been in progress for a while. Those in favor of traffic circles say that, among other things, ...
7 votes
1 answer
2k views

How are train crossing signals and highway traffic signals coordinated?

Some roadway intersections that are near railroad tracks have signs that light up when a train is approaching. These signs warn that certain turns are not allowed because of the train. One of these ...
3 votes
1 answer
197 views

How can traffic signal controllers handle multiple conflicting preemption requests of equal priority without dropping one?

Let us assume that we are North American traffic engineers, and have the (hypothetical, plausible, yet pathological) intersection configuration depicted (not to scale and lacking lane lines, sorry -- ...
4 votes
2 answers
492 views

What is the starting/stopping sequence of a traffic light

As is probably known a traffic light may be turned off in which case normal rules applies to the intersection. While the traffic light is active then red & red+yellow means that drivers are ...
0 votes
1 answer
180 views

What are the disadvantages of free-flow intersections?

I've recently learned about free-flow intersections. In particular, the DCMI, and the Stack interchanges. What are the disadvantages of using them, compared to the "normal" signaled intersections? do ...
2 votes
2 answers
306 views

How can a sensor detect the traffic lights? [closed]

I am working on an idea for my capstone project. I am trying to get an idea of a device, sensor or reader that can detect the front traffic light situation. so that it can tell when the light is green ...
19 votes
3 answers
16k views

How does a traffic light sense the proximity of vehicles?

Some traffic lights don't operate periodically but instead detect when a car is close by and then turns green. I have heard that they use a magnetic sensor embedded in the road to sense cars as they ...