Liikennevalaisimet

Liikennevalaisimet, commonly known as traffic lights, are signaling devices positioned at road intersections, pedestrian crossings, and other locations to control competing flows of traffic. They use colored lights, typically red, yellow (or amber), and green, to indicate when vehicular or pedestrian traffic should stop, prepare to stop, or proceed.

The primary purpose of traffic lights is to improve traffic safety and efficiency. By assigning the right-of-way to different traffic streams in a cyclical manner, they reduce the likelihood of collisions that can occur at uncontrolled intersections. They also help to optimize traffic flow, minimizing delays and congestion, especially in urban environments.

The standard sequence for traffic lights involves a cycle starting with green, allowing traffic to proceed. This is followed by yellow, which warns drivers that the light is about to turn red and they should prepare to stop if safe to do so. Red then prohibits traffic from entering the intersection. In some systems, a flashing red light functions similarly to a stop sign, requiring a complete stop before proceeding if safe. A flashing yellow light indicates caution, allowing traffic to proceed without stopping but with due care.

Traffic light systems can range from simple, fixed-time controllers to sophisticated, adaptive systems that use sensors to detect traffic volume and adjust signal timing in real-time. Pedestrian signals, often integrated with vehicle traffic lights, use symbols of a walking person (green) and a raised hand (red) to guide pedestrian crossing. The design and implementation of traffic lights are crucial elements in modern transportation engineering.