At every city intersection, a “silent conductor” stands vigil—the traffic signal. Through the alternating sequence of red, yellow, and green lights, it regulates the flow of vehicles and pedestrians, serving as a core facility for road safety.
But do you truly grasp all its rules? The difference between arrow lights and full-screen lights, the taboos of proceeding when the yellow light flashes, priority principles in special scenarios... These details concern not only traffic order but also life safety. Today, we comprehensively deconstruct the rules and meanings of traffic signals.
The world's first traffic signal emerged in London, England, in 1868. At that time, London's streets were chaotic with horse-drawn carriages, pedestrians, and vehicles sharing the road, leading to frequent congestion and accidents. Engineer John Peake Knight designed a mechanical lever-operated signal using red and green gas lamps, manually controlled by police officers.
However, this system was soon discontinued after a gas leak explosion injured an officer. Despite this setback, it laid the foundational prototype for modern traffic signals.
In the early 20th century, Detroit police officer William Poots introduced a yellow signal as a “transition warning” alongside the existing red and green lights, establishing the red-yellow-green triad still in use today.
Today, traffic lights have evolved from mechanical devices to LED smart lights. Not only do they offer higher brightness and longer lifespans, but they also enable “adaptive timing” through traffic flow detection, significantly boosting intersection efficiency.
Among visible light, red light possesses the longest wavelength (620-750nm) and strongest ability to penetrate air and fog. It remains visible at long distances in adverse weather, making it the ideal choice for “stop” signals to ensure warning effectiveness.
Green light, with a moderate wavelength (495-570nm), offers high visual comfort and stark contrast against red, enabling drivers to distinguish it quickly. This naturally makes it the signal for “proceed.” Yellow light, positioned between red and green with high brightness, serves as the ideal “warning transition” signal.
After a century of application, the meanings of red, yellow, and green have become universally accepted traffic conventions worldwide. People instinctively perceive “stop” when seeing red light and form a conditioned reflex of “proceed” upon seeing green light. This consensus significantly reduces traffic communication costs.
When the red light is on, vehicles must stop behind the stop line and must not cross it into the intersection. Pedestrians and non-motorized vehicles must also wait in safe areas and are prohibited from entering crosswalks or intersections.
Special Note: Vehicles that crossed the stop line before the red light turned on may proceed without being considered a red light violation. However, crossing the stop line after the red light turns on constitutes a violation.
When the green light is on, vehicles and pedestrians may proceed normally through the intersection according to their direction of travel. However, drivers must observe pedestrians and non-motorized vehicles at the intersection, as well as any turning vehicles that may interfere, ensuring safety before proceeding.
For right-turning vehicles, even with a green light, yield to pedestrians crossing the crosswalk and vehicles proceeding straight.
A yellow light indicates an imminent signal change. The core rule is: “Proceed if already over the line; stop if not yet over the line.”
If a vehicle has already crossed the stop line or entered the center of the intersection before the yellow light appears, it may proceed. If the vehicle is still behind the stop line and has sufficient distance to stop, it must stop and wait. Accelerating to rush through is strictly prohibited. When the yellow light flashes (at some intersections), it indicates “Caution: Safety Alert.” Vehicles must slow down and proceed only after confirming safety.
Arrow signals provide more precise directional guidance than full-screen lights, explicitly granting passage rights for “a specific direction.” Common types include left-turn, straight-through, and right-turn arrow lights.
Core Rule: Vehicles may proceed only when the corresponding directional arrow light is green. If the arrow light is red, vehicles are prohibited from proceeding in that direction even if the full-screen light is green. For example, when the left-turn arrow is red, vehicles must not turn left and must wait for the arrow light to turn green.
Flashing warning lights are typically yellow and commonly installed at intersections near schools, residential areas, or accident-prone zones. They indicate “Look out carefully and proceed only after confirming safety.”
When approaching such intersections, drivers must slow down, observe surrounding pedestrians and vehicles, yield to those with right-of-way, and avoid rushing to proceed, which could cause accidents.
Lane signal lights are positioned above lanes, using green arrows or red cross-shaped lights to indicate lane availability. A green arrow indicates the lane is open for normal passage, while a red cross indicates the lane is prohibited (e.g., due to temporary closure or lane configuration adjustments).
For example, at highway entrance lane signals, vehicles must not enter the lane when the red cross is illuminated.
If signals malfunction—e.g., flashing erratically or failing entirely—intersections must be navigated as if uncontrolled. Core principles are “yield to the right” and “turns yield to straight-through traffic”: vehicles approaching from opposite directions must yield to those on the right; turning vehicles must yield to straight-through traffic.
Per the Road Traffic Safety Law, on-site police direction takes precedence over traffic signals. Even if signals conflict with officer instructions, vehicles and pedestrians must obey police commands.
Example: If a red light is displayed but an officer signals vehicles to proceed, drivers may follow the officer's direction through the intersection.
A red railroad crossing signal indicates an approaching train, accompanied by lowering barriers. Vehicles and pedestrians must stop beyond the safety line. Climbing over barriers or rushing through is strictly prohibited.
If the signal flashes as a warning, it means a train is imminent. Immediately stop and wait until the signal stops flashing and the barriers rise before proceeding.
In China, penalties for traffic signal violations primarily target actions like “running red lights” and “disregarding directional arrows”:
— Running a red light: 6 demerit points, 200 yuan fine;
— Disregarding directional arrow signals (e.g., turning left when the left-turn arrow is red): 3 demerit points, 200 yuan fine;
— Crossing the stop line while proceeding through a yellow light: Some regions issue warnings or impose 100 yuan fines.
Data shows nearly 30% of intersection accidents in China involve traffic signal violations. Vehicles running red lights often travel at high speeds, causing severe collisions with other vehicles or pedestrians that can result in serious injury or fatalities.
Pedestrians jaywalking at red lights pose equal danger. When suddenly entering an intersection during a green light for vehicles, drivers often lack time to react, leading to instant tragedy.
Observe signal status 50-100 meters before intersections. If green is ending, slow down early to avoid rushing through yellow lights. When seeing arrow signals, plan lanes ahead to prevent illegal lane changes.
Special Note: Large vehicles have blind spots due to “inner wheel difference.” Maintain a safe distance from them even when proceeding on a green light.
Pedestrians must use crosswalks and wait for the pedestrian green light before crossing. Do not jaywalk or run red lights. Non-motorized vehicles (e-bikes, bicycles) must obey motor vehicle signal rules and must not occupy motor vehicle lanes to rush through on red lights.
Elderly individuals, children, and visually impaired persons may utilize intersection aids such as pedestrian crossing audio signals and tactile paving to confirm signal status and road conditions before crossing. Seek assistance when necessary.
Every color and every flash of a traffic signal embodies the rules and responsibility of “safe passage.” It is not a constraint, but a safeguard for every road user.
Whether you are a driver, pedestrian, or non-motorized vehicle rider, understanding and obeying traffic signal rules is not only a basic legal requirement, but also a sign of respect for your own life and the lives of others.
Let us begin at every intersection: honor traffic signals, follow the rules, and collectively foster a safe, orderly, and efficient road environment. If you are involved in traffic facility construction or maintenance and require high-quality, reliable traffic signal products, please contact us. We will provide professional products and services to build a solid foundation for road safety.
