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One Glance Determines Direction! Signal Light: Make Every Turn A Safety Declaration

2025/11/24

Every flicker of a turn signal is a safety dialogue between the driver and the road.
In the long history of automotive development, signal lights have always served as the silent language of communication between vehicles and the outside world. Among these, turn signals stand as the most crucial light-signaling devices, transforming drivers' intentions into clear visual signals through their distinct flashing rhythm, providing valuable anticipation time for surrounding vehicles and pedestrians at critical moments.
This seemingly simple flashing device embodies a deep integration of century-long technological evolution and safety philosophy. From initial hand gestures to today's intelligent light-signaling systems, the development of turn signals represents nothing less than an evolutionary history of automotive safety technology.
The Silent Language of Safety: The Importance of Turn Signals
Turn signals are fundamentally vehicle dynamic information transmission devices. Through their alternating bright and dark flashes, they effectively indicate the direction of a vehicle's turn or lane change. These flashing lights, positioned at the front, rear, and sides of a vehicle, form a communicative bridge between the vehicle and its surroundings.
The core value of turn signals lies in the crucial decision-making time they provide to road users. Research indicates that when a vehicle suddenly turns or changes lanes while moving, timely activation of turn signals can save following drivers approximately 1-2 seconds of reaction time—which often translates into several meters of safety distance at high speeds.
It's important to note that using turn signals is not merely a driving habit but a legally mandated safety obligation. According to the "Implementation Regulations of the Road Traffic Safety Law," vehicles must use turn signals as required during operations such as lane changes, turns, and U-turns. Failure to use turn signals as stipulated constitutes a traffic violation and is subject to corresponding penalties.
From Gestures to Light Language: The Development History of Turn Signals
In the early days of the automobile, there were no dedicated signaling devices. Historical records show that in 1916, a man named C.H. Thomas mounted a battery-powered bulb on his glove to allow other drivers to see his hand signals at night—a humorous debut for the turn signal.
In 1938, American Buick automobiles first installed flashing turn signals, though initially only as optional accessories mounted on the rear of the car. It wasn't after 1940 that turn signals became commonly installed at the front of vehicles, forming a complete front-and-rear signaling system.
The development of turn signal technology in China has similarly progressed from introduction to independent innovation. In recent years, with the implementation of national standards such as GB 5920-2024 "Light Signaling Devices and Systems for Motor Vehicles and Trailers," China's turn signal technical specifications have aligned with international advanced standards.
This new standard was released on September 29, 2024, and is scheduled to take effect on July 1, 2025, replacing previous standards including GB 5920-2019. It establishes more stringent and detailed regulations for the technical requirements, testing methods, and inspection rules of turn signal lights.
The Science Behind the Flash: How Turn Signals Work and Their Types
The turn signal system primarily consists of three main components: the turn signal lights, the flasher unit, and the turn signal switch. Among these, the flasher unit is the core component controlling the light flashing, determining the turn signal's flash frequency and stability.
The Working Mechanism of the Flasher Unit
The development of flasher units has evolved from simple mechanical to intelligent electronic systems. Early vehicles commonly used thermal (electro-thermal) flashers, which operated on the principle of current thermal effect, using thermal expansion and contraction as power to create sudden movements in spring plates, thereby connecting and disconnecting contacts to achieve light flashing.
Subsequently, capacitor-type flashers emerged, working by utilizing the charging-discharging delay characteristics of capacitors to cause the two coils of the relay to generate varying electromagnetic attraction. This created periodic switching actions in the relay, resulting in turn signal flashing.
Modern vehicles widely adopt electronic flashers, which use the switching characteristics of transistors and the charging-discharging delay characteristics of capacitors to control the relay coil's on-off state, connecting or disconnecting contacts to make the turn signals flash. Electronic flashers are widely used in modern automotive turn signal systems due to their reliability and long service life.
Comparison of Different Types of Turn Signals
Based on different light source materials, turn signals can be mainly divided into two categories: gas discharge automotive turn signals and LED automotive turn signals.
Gas discharge turn signals (such as halogen lamps) feature mature technology and lower prices, but they have disadvantages including slow response speed, high power consumption, and relatively short lifespan. Furthermore, their glass housings are prone to breakage, and the mercury they contain can cause environmental pollution.
LED turn signals, on the other hand, offer advantages such as being pollution-free, long service life (theoretically reaching 50,000 hours, meaning no bulb replacement throughout the vehicle's lifespan), and fast response speed. LEDs illuminate one-fifth of a second faster than incandescent bulbs. When a car travels at 105 km/h, it covers 5.8 meters in 1/5 of a second, providing extra time and space for drivers to avoid other vehicles. However, LED automotive turn signals are more expensive, which has somewhat limited their widespread adoption.
Regulations and Safety: Standardization Requirements for Turn Signals
As critical components for vehicle safety, turn signal technical specifications are strictly constrained by national mandatory standards. The GB 5920-2024 standard covers 13 categories of light signaling devices used in M, N, and O category vehicles, including front position lamps, rear position lamps, turn signal lamps, stop lamps, and others.
The new standard introduces more refined technical requirements for turn signals, for example:
Clarified standards for sequential turn signals, specifying the flashing sequence and frequency of turn signal lamps.
Added specifications for light signal projection functions, allowing turn signals to project simple geometric patterns or single letters, but requiring synchronization with the signal light sequence.
Specified colorimetric requirements for turn signals, ensuring accurate and consistent signal color.
The formulation of these technical specifications aims to enhance the recognizability and reliability of turn signals under various environmental conditions, maximizing their safety warning function.
Proper Use of Turn Signals: A Key Aspect of Safe Driving
Using turn signals appropriately is not only a matter of traffic safety but also reflects the driver's professionalism and sense of road responsibility. Turn signals must be activated in the following situations:
At planar intersections: Turn signals should be activated in the intended direction of travel, 30-10 meters before reaching the intersection.
When changing lanes: Drivers should first observe adjacent lanes via mirrors and activate the corresponding turn signal when it does not hinder the normal movement of other vehicles.
At roundabouts: The appropriate turn signal should be activated based on the intended direction of travel.
When pulling over to park: The right turn signal should be activated in advance, while paying attention to traffic dynamics behind and to the right of the vehicle.
It is important to note that turn signals should not be activated too early or too late—activating too early may give following vehicles the impression that the driver forgot to turn off the signal, while activating too late can cause following vehicles or pedestrians to react inadequately, potentially leading to accidents.
Future Prospects: Intelligent Turn Signal Systems
As vehicles become increasingly intelligent, turn signal technology continues to innovate and break new ground. The widespread adoption of LED technology has brought more possibilities for turn signal design. LED sources used in modern vehicles, with their microsecond-level response speed, significantly improve warning effectiveness compared to traditional incandescent bulbs.
The emergence of side mirror turn signals has further enhanced driving safety. Since the lights in these mirrors are LEDs, the system offers additional advantages: LEDs illuminate one-fifth of a second faster than incandescent bulbs. Side mirrors are an ideal location for turn signals because when another car is in your blind spot, the other driver might not see the turn signals on your car's rear.
Light signal projection technology is another innovation, allowing vehicles to project turn signals onto the road surface, creating a distinct visual area. According to the GB 5920-2024 standard, this light signal projection function can adjust the projection angle when triggered by obstacles around the vehicle, or even automatically shut off.
In the future, with the development of vehicle-to-everything (V2X) and autonomous driving technologies, turn signals will no longer be merely communication tools between human drivers but will become important interfaces for interaction between vehicles and intelligent transportation systems. The coordination between turn signals and ADAS (Advanced Driver-Assistance Systems), such as automatically activating turn signals during automated lane changes, will further enhance road safety assurance capabilities.
As one of the most basic yet vital safety devices in vehicles, turn signals silently guard every turn and lane change with their simple, clear flashing language. In increasingly complex road environments, correctly using and understanding turn signals is not only compliance with the law but also respect for life.
When we activate the turn signal lever guided by the steering wheel, that flickering amber light is more than just a mechanical flash—it is our safety declaration to the road. This is the driver's responsibility and a manifestation of modern traffic civilization.

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