Traffic signal lights are not only the core component of the traffic signal system, but also the basic “language” of road traffic. Its core consists of red, green and yellow lights: the red light represents the prohibition of traffic, the green light indicates the permission to pass, and the yellow light plays the role of signal conversion warning. In addition to the basic three-color lights, the traffic signal also contains non-motorized signals, pedestrian crossing signals, lane signals and other subdivided types, covering the needs of motor vehicles, pedestrians, public transportation and other types of road users.
Traffic lights
Traffic signal light realizes the precise management of intersection order through intelligent controller, which is mainly applied to key nodes such as crossroads and T-junctions. Its core functions include: strengthening road traffic management efficiency, reducing the incidence of traffic accidents, improving the utilization of road resources, and optimizing the overall traffic operation. According to the World Health Organization, standardized traffic signals can reduce the accident rate at intersections by 30%-50%, making them an indispensable safety cornerstone of modern traffic systems.
A green light is a clear signal that gives the right of way, whether it’s a driver starting his vehicle and continuing on his way, or a pedestrian crossing the street at a crosswalk. But the prerequisite for passing is vigilance – according to the Regulations for the Implementation of the Road Traffic Safety Law, turning vehicles are required to yield to vehicles and pedestrians traveling straight ahead, reflecting the balance between “freedom of movement” and “duty of safety”. “ balance.
In the field of intelligent transportation, the value of green lights is further amplified. For example, in many cities, the “Green Belt” system is used during off-peak hours to synchronize the green light times of multiple intersections, allowing vehicles to pass through intersections continuously at a constant speed, reducing fuel consumption by 30% and travel time by 20%, and significantly improving the smoothness of the road.
Red is the most authoritative of all traffic signals, requiring all vehicles and pedestrians to stop immediately to make safe space for traffic flowing in the other direction. This mandatory stop reduces the risk of collisions at intersections – studies have shown that red light rules can reduce conflict points at intersections by more than 80%.
It is important to note that red lights are not an absolute ban on traffic. On the premise of not obstructing other road users, right-turning vehicles can pass cautiously, a design that ensures safety while balancing traffic efficiency. For example, in cities that have adopted the “right turn on red” rule, intersections can be 15-20% more efficient, but accidents need to be avoided through clear signage and driver education.
Traffic lights
The yellow light serves as a “transition” between red and green, both as a warning and as a buffer. When a yellow light is on, drivers have a very short time to determine whether they can safely cross the intersection or brake in time. Scientific studies have shown that a reasonably set yellow light duration (usually 3-5 seconds) can reduce rear-end accidents caused by emergency braking by 40%, while avoiding red-light running accidents triggered by forceful rushing of the light.
From the legal point of view, the yellow light requires vehicles to stop as far as possible in front of the stop line, but if they have already crossed the stop line, they can continue to pass; if pedestrians have entered the crosswalk, they need to speed up to pass or return to the safety zone. This rule is a flexible response to actual road conditions and balances the need for both safety and access.
In addition to the traditional three-color lights, some cities have introduced white lights to manage Bus Rapid Transit (BRT) lanes. White lights are usually presented in the form of horizontal or vertical strips to indicate the passing, yielding or stopping of BRT vehicles. For example, the Shenzhen BRT system uses white light signals to separate buses from social vehicles, increasing the speed of buses by 40%, increasing punctuality to 95%, and avoiding signal confusion in mixed lanes.
| Signal Type | Applicable Users | Typical Shape | Core Function |
| Traditional Three-Color Light | All Road Users | Circular Light | General Passage /
Prohibition / Warning |
| White Light | BRT Vehicles | Horizontal / Vertical Bar Light | Dedicated Lane Control, Separating Public Transit from General Traffic |
Traffic signals significantly reduce intersection risk through a standardized system of commands. Data shows that at signalized intersections, collisions due to jaywalking are reduced by 65% compared to unsignalized intersections, and pedestrian crossing safety is improved by more than 50%. The core mechanism is: through clear “right of way allocation” (such as green light phase allocation of different directions of the passage time), the complexity of the intersection conflict into an orderly time sequence, to fundamentally reduce human error in judgment.
Traffic lights
Efficient signal timing is the key to relieve congestion. Taking Chaoyang Road in Beijing as an example, by intelligently optimizing the signal cycle, the peak hour traffic volume increased by 28% and the average waiting time was shortened by 19 seconds. The role of signals is not only reflected in “flow control”, but also “peak shaving” – by adjusting the length of green light in different directions, the traffic flow can be dynamically balanced to avoid excessive backlog in a single direction. The effect is especially significant on roads with obvious tidal phenomena.
Pedestrian signals are designed to work in tandem with motor vehicle lights to provide a safety barrier for the vulnerable. For example, pedestrian crossing signals are usually provided with “pre-green” (pedestrians start before motor vehicles) and “extended green” (to ensure that long distance crossing is completed), which together with the “stop and yield” rules of motor vehicles in crosswalk zones, can enable pedestrians to cross the street. “ rule in zebra crossing areas can reduce pedestrian crossing accidents by 70%. In cities such as Tokyo, pedestrian-only green light phases even prohibit motor vehicles altogether, maximizing crossing safety.
Traffic signals play an important role in environmental protection by reducing inefficient energy consumption. Studies have shown that optimized signals can reduce the average idling time of vehicles by up to 35%, with a corresponding reduction in CO2 emissions of 12-18%. Taking the center of Berlin, Germany as an example, through the intelligent “Green Belt” system and dynamic traffic data linkage, the average annual carbon emission reduction in the region reaches 1,800 tons, which is equivalent to planting 100,000 adult firs. This demonstrates that intelligent traffic management not only reduces congestion, but also plays a real role in combating climate change by reducing fossil fuel consumption and the carbon footprint of cities.
Traffic lights
Modern signaling systems can be linked with emergency vehicles to create an “emergency green wave” for fire trucks, ambulances, etc. through GPS positioning and wireless communication. For example, when New York City’s EMS system was connected to signals, the average ambulance response time was reduced by 1 minute and 23 seconds, a time difference that increased survival rates for cardiac arrest patients by 10-12 percent. This type of technology is spreading from first-tier cities to small and medium-sized cities, and is becoming an important safeguard for “life lanes”.
With the development of smart cities and autonomous driving technology, traffic signals are moving from “timing control” to “intelligent sensing”, and AI algorithms can analyze real-time data on traffic and pedestrian flow to dynamically adjust signal timing – such as Singapore’s “City Traffic Engine”. – AI algorithms can analyze traffic and pedestrian flow data in real time and dynamically adjust signal timing – such as Singapore’s Urban Traffic Engine (UTEP) system, which uses camera and sensor data to improve intersection efficiency by 30%.
More far-reaching changes come from Vehicle-to-Circuit (V2X) technology: self-driving vehicles interact with signals in real time, can predict signal changes and optimize driving paths, which theoretically can increase intersection traffic efficiency by more than 50%, while completely eliminating red-light running accidents due to visual blind spots. In the future, the signal light may become the terminal node of the “traffic brain”, linking with drones, shared bicycles and other elements to build a zero-congestion, zero-accident intelligent transportation network.
Traffic signal light is not only a set of luminous equipment, but also the epitome of modern urban civilization — it uses color as the language and time sequence as the rule, which reflects the respect for life, responsibility for the environment, and imagination for the future while guaranteeing safety and efficiency. From the three-color light on the street corner to the intelligent system in the cloud, this transportation revolution that has lasted for a hundred years is leading mankind to a safer, more efficient and more sustainable travel future.
