Smart traffic lights work using two main mechanisms: timers and sensors. In large cities around the world where traffic is constant, traffic light systems often use fixed timers. Meanwhile, in the suburbs or on roads with less traffic, sensors are preferred because of their ability to accurately detect the number of vehicles at the intersection and adjust the light time accordingly.
According to Automate Systems, a UK-based transport infrastructure solutions company, traffic sensors have been applied with a variety of technologies, including magnetic loops, radar, cameras, lasers and gas-filled rubber tubes to support traffic light systems.
Induction coils are the most common technology used in traffic light systems. These are coils buried in the roadway that operate based on changes in magnetic fields as vehicles pass by.
When a vehicle changes the magnetic field, a signal is sent to the traffic signal controller, which changes the light status. Magnetic loops have the advantage of being stable, unaffected by weather, and having few errors. However, they can have difficulty detecting bicycles due to the small amount of metal on the bike.
Microwave radar sensors are becoming increasingly popular, replacing magnetic loops in some cases. Microwave radar detects large objects moving within a certain range at a minimum speed of 5 km/h.
They are easier to install and have lower maintenance costs than magnetic loops. However, in areas with harsh weather conditions or overhead obstructions, magnetic loops are still the preferred choice.
Detection cameras are also used in modern red light systems. These cameras are mounted on poles and connected to specialized software to identify vehicle detection zones.
They are especially useful in places where magnetic loops cannot be installed, such as on rough or gravel roads. However, video cameras have the disadvantage of being susceptible to bad weather, headlights, and shadows from cars in the adjacent lane, leading to false signals.
In addition, other technologies such as geomagnetic sensors, laser sensors and radar sensors are also used in specific situations. Magnetic sensors detect changes in magnetic fields, laser sensors measure the distance from the vehicle to the intersection, and radar is often used to detect pedestrians thanks to its ability to detect movement.
These technologies not only help improve traffic flow but also increase safety at intersections. For each specific location, the choice of technology will be based on operating conditions and the most suitable cost.
