Do traffic signals have weight sensors, or is it just a timer that changes the light?

Answer 1

They're not weight sensors, they're metal sensors.

Look in the road near an intersection. If you see cut-corner squares scored into the pavement, with additional scored cuts heading back toward the control box, those are sensors. Basically they're big coils of wire embedded in the pavement. When a large ferrometallic object, such as a car, passes over them, it induces an electrical current in the coil. The control box reacts to this current and changes the lights.

If there is no car traffic, the lights revert to a timer, so that bicycles and pedestrian traffic can get their chance.

Answer 2

At last, a question where I am expert. I have worked on traffic signals for the last 22 years.

It is true that some traffic signals operate solely off of a timer but, with the enormous increase in traffic in urban areas they are becoming rare.

The most popular form of vehicle detection today is the inductive loop. It is a loop of wire embedded in the pavement and is usually between 30 and 90 feet long, six feet wide and is centered in the lane of traffic at the intersection. When a vehicle pulls up on this loop it changes the inductance of the loop and sends a signal to the controller (timer) and the controller recognizes there is a vehicle on that approach to the intersectin awaiting a green light and will (eventually) give that vehicle a green light.

With modern technology the inductive loop is slowly approaching the end of its life-cycle and is being replaced by video cameras that serve the same purpose as an inductive loop. Cameras, pointed at the different approaches to the intersection, have vehicle detection zones programmed into them. When a vehicle enters that zone the processor for the camera measure the percentage of change in the pixels and sends a signal to the controller which will cause the same actions as an inductive loop.

Answer 3

Most traffic sensors are magnetic – look for strips in the road in the shape of rectangles or diamonds. On night timing the sensors may change the light immediately, but otherwise the sensor just allows the traffic control system to know whether a car is waiting to pass, or how long the backup is, so it can know when to change the light.

Answer 4

They do have weight sensors for when traffic is lite the sensors will automatically switch from the timer mode which also changes depending on what part of the day

Answer 5

Most traffic lights do not have sensors. They are typically controlled by a green box near the intersection that changes the light at periodic intervals. If you stand near one, you can hear the relays clicking as the light changes. However, there are lights that have poles near the intersection that contain sensors to detect cars and change the lights accordingly. These are place in areas where there tends to be little traffic coming out of these roads.

Answer 6

Timers. Ar times you will see police with remotes changing signals to improve traffic flow. Genereally weight sensors are used with security gates...

Answer 7

In the old days they had weight sensor, today they use a magnetic loop. If your car is all alunimum, then you are out of luck! If you look at the ground when you approach an intersection, you'll notice large circles in the asphalt. If you stop your car where the largest amount of metal is inside those wire loops, the light should eventurally change for you. Many lights are timed and the loops have no effect during certain times of the day. Many are exclusively ran by the loops and ONLY work when it 'sees' a car at the intersection. As a motorcycle rider I watch for these loops and try to stop directly in the middle.

Answer 8

It depends on the place or traffic volume or type of TCD (traffic control device) for the less used smaller intersection it has a motion sensor, but for big intersections you use a timer

Answer 9

Some have weight sensors but it's mainly a timer.

Answer 10

A timer that changes the light.