How does the logic gates operate in traffic lights?

Question

How does the logic gates operate in traffic lights?

Answer 1

All computers have a very small set of basic logic gates; AND, OR, NOT, XOR. An AND gate is a circuit whose output is turn on when both of its two inputs are turned on. An OR gate turns on the output if at least one of its inputs is on. A NOT gate turns on the output when the input is off and vice versa. An XOR gate turns on the output when only one of its inputs is on.

Combining those basic gates, you can make adders, multipliers, counters and even language translators and programs that talk to you in your own language.

That's how most computers work.

Answer 2

I would expect that no current traffic controller uses logic gates.  Almost all of them use microcontrollers which are often fed information over phone lines besides having a default behavior when connection fails.   Having a microcomputer means that different cycles can be used at different times of day and the phone line means that the signal can be synched with lights several blocks up and down the street or can be adjusted to increase traffic flow in a particular direction because of an accident on a nearby street or a big event like a football game letting out.

  Unless the controller is on a fixed cycle, each intersection and lane has sensors that determine if a car is waiting over them.  They may also report cars passing over them without stopping to determine traffic load.  The controller uses rules to keep all the traffic from various directions moving - just because there are constantly cars on the main drag doesn't mean they always get a green, a waiting car on the side street gets to go after a not unreasonable time (otherwise drivers tend to run red lights assuming it will never change.)

  The most common patterns for intersections are letting cars facing each other go together with allowance for left turns or doing a rotating cycle where one direction goes at a time and sees lights throughout the intersection to clear it

Answer 3

A fair amount of traffic lights look for a length of time where no cars have passed along their view, and whether or not there are cars in the opposite direction. Once a predetermined time has been reached where no cars have passed through the sensors, the lights begin to trip.

On the other side of the coin, the lights are timed to switch with heavy traffic after a certain amount of time, and they will always switch this way due to the programming, regardless of how many cars pass through.

So if you're coming to an intersection, and there's noone in front of you for quite a ways, but there are people in the cross traffic, there's a good chance that by the time you reach the light, it'll have started to change. =)