Trip

How do the trips at a traffic light work?

The trips I am refering to are the metal wires that are in the road directly in front of the traffic light. They sense when a vehicle is there.

Public Comments

1. weight of the vehicle
2. Here is the low down: sensors sensors all the way. hope this is helpful to you.There is something exotic about the traffic lights that "know" you are there -- the instant you pull up, they change! How do they detect your presence?
   
   
   
   Some lights don't have any sort of detectors. For example, in a large city, the traffic lights may simply operate on timers -- no matter what time of day it is, there is going to be a lot of traffic. In the suburbs and on country roads, however, detectors are common. They may detect when a car arrives at an intersection, when too many cars are stacked up at an intersection (to control the length of the light), or when cars have entered a turn lane (in order to activate the arrow light).
   
   
   
   There are all sorts of technologies for detecting cars -- everything from lasers to rubber hoses filled with air! By far the most common technique is the inductive loop. An inductive loop is simply a coil of wire embedded in the road's surface. To install the loop, they lay the asphalt and then come back and cut a groove in the asphalt with a saw. The wire is placed in the groove and sealed with a rubbery compound. You can often see these big rectangular loops cut in the pavement because the compound is obvious.
3. What you are referencing are inductive loops that are placed in the pavement. They work on the theory of inductance that is caused by a large mass of metal passing over the loops.