What Are Traffic Lights (Lichtsignalanlagen)?Traffic lights, known as "Lichtsignalanlagen" (LSA) in Swiss traffic law, are critical control devices installed at intersections, pedestrian crossings, and other key points to regulate the movement of traffic. They use a system of colored lights – typically red, yellow (amber), and green – to assign right-of-way and ensure orderly progression. Understanding these signals is paramount for every driver, as they override general priority rules and other road signs.## The Purpose and Importance of Traffic LightsTraffic lights are implemented for several reasons, primarily to enhance road safety and optimize traffic flow. By clearly assigning who can proceed and who must stop, they help prevent collisions at busy junctions and reduce congestion. For driving theory exams, knowing the precise meaning and required actions for each signal is a core component, often featuring in questions related to priority and hazard perception.## Standard Traffic Light Signal SequencesThe most common traffic light sequence controls vehicle traffic with three distinct phases:

• Red Light: Indicates "Stop." Vehicles must halt before the stop line and are not permitted to enter the intersection. In Switzerland, as in many European countries, a steady red light always means stop.

• Red and Yellow Light (simultaneously): This phase immediately follows red and precedes green. It means "Prepare to go." Drivers should get ready to move, but must not start until the green light appears. This phase is common in Switzerland, Germany, Austria, and other European nations.

• Green Light: Indicates "Go." Traffic is permitted to proceed, provided the intersection is clear and it is safe to do so. Even with a green light, drivers must still yield to pedestrians and cyclists crossing their path, and to oncoming traffic when turning left, unless specifically directed by a green arrow.

• Yellow Light (following green): Indicates "Prepare to stop." This light appears after green and before red. Drivers should stop if it is safe to do so. If stopping would cause a dangerous situation (e.g., a sudden brake causing a rear-end collision), a driver may proceed cautiously. The yellow phase acts as a clearing time for the intersection.## Special Traffic Light Signals and ApplicationsBeyond the standard three-color signals, various specialized traffic lights cater to specific situations and road users:

• Flashing Yellow Light: If a traffic light is flashing yellow, it indicates that the signals are out of operation or operating under special conditions (e.g., at night during low traffic). In such cases, drivers must exercise extreme caution and observe general priority rules (e.g., right before left, or priority signs).

• Flashing Red Light: Primarily used at railway crossings in Switzerland (Art. 93 Abs. 2 SSV), it means "Stop." A flashing red light requires drivers to stop and wait until the light stops flashing and it is safe to proceed.

• Green Arrows: A green arrow within a traffic light, or a separate green arrow signal, indicates that traffic may proceed in the direction of the arrow. If it's a dedicated arrow, it often means oncoming or crossing traffic has a red light, granting protected movement. If a green arrow is flashing alongside a yellow light, as mentioned in Art. 68 Abs. 3 SSV, turning vehicles must still yield to oncoming traffic, pedestrians, and cyclists.

• Pedestrian Signals: These lights typically show a standing red figure ("Don't Walk") and a walking green figure ("Walk"). Pedestrians must only cross when the green figure is illuminated. Some pedestrian signals may also feature a flashing green or yellow phase, or a countdown timer, to indicate that the "Walk" phase is ending.

• Cyclist Signals: Where dedicated cycle paths exist, cyclists may have their own signals, often featuring a bicycle symbol. These generally follow the same red, yellow, green sequence but are timed specifically for cyclists.

• Public Transport Signals: In Switzerland, trams and buses on dedicated lanes often have their own unique signals, known as "Punktesignale" (dot signals). These typically show white dots in various arrangements (e.g., a horizontal bar for stop, a vertical bar for straight ahead, diagonal bars for turns) to prioritize public transport.## Legal Framework in SwitzerlandIn Switzerland, traffic lights are legally defined as "Lichtsignalanlagen" (LSA) and their operation and meaning are detailed in the Signalisationsverordnung (SSV). Article 68 SSV outlines the types and meanings of light signals, stating that they take precedence over general priority rules, priority signs, and markings. It also clarifies that even with a green light, turning vehicles must yield to oncoming traffic, pedestrians, and users of similar devices on the crossing road.## What to Do When a Traffic Light FailsIf a traffic light is out of order or malfunctions, it will often display a flashing yellow light or be completely dark. In such situations, drivers must treat the intersection as if it were unregulated and strictly adhere to all other road signs (e.g., stop signs, yield signs) and general priority rules, such as "right before left."