Published : 17/11/2025
When you travel by high-speed train in China, have you ever noticed that its headlights are always on, even when the train is running in daylight? Isn't that a waste of electricity?
For both illumination and warning
The core reason why high-speed trains keep their headlights on during the day is for safety.
As the train travels at high speed between different provinces and cities, it may encounter weather that reduces visibility along the way, such as heavy rain or dense fog, and may also have to pass through tunnels, so keeping the headlights on at all times can provide more stable illumination for the train, preventing a sudden darkening of the view ahead that could affect the driver's line of sight.
At the same time, switching on the headlights also serves as a warning.
Railway signals are divided into audible signals and visual signals. The train's horn is a type of audible signal, used for example to inform station staff that the train is entering the station, or to remind waiting passengers to keep a distance from the platform edge.
Read more: Why does the first high-speed train of the day not carry passengers?
High beams illuminate up to 2 km
However, just sounding the horn is not enough, and switching on the headlights is also necessary because light travels faster than sound. Before the sound of the train's horn arrives, people will see the headlights first, which is the light signal used to warn that the train is coming.
Friends who drive will know that car headlights have high beams (full beams) and low beams (dipped beams). Do high-speed trains have them as well?
Indeed they do, however, the train keeps its high beams on throughout its journey so that the driver can see the track and signal information further ahead. As for low beams, which cars generally use more often, high-speed trains only use them when entering the depot for maintenance to avoid causing glare for ground crew.
You may not know that a car's high beams have an illumination range of about 100 to 150 metres, whereas for a high-speed train, because its speed is so high and the surroundings flash by in an instant, its high beam illumination distance can reach two kilometres, ensuring the driver has sufficient distance to observe and react.
How far is two kilometres? Walking at a normal pace, you can cover about two kilometres in half an hour.
Carriage lighting for greater passenger comfort
Friends with driving experience might also ask: if a high-speed train keeps its high beams on all the time, will it interfere with the driver of an oncoming train?
No, it won't, because the high beams on high-speed trains are mostly located in the centre of the train's front, with some near the top in the centre, so their illumination range is more focused and will not affect other trains.
In addition, on a moving high-speed train, the lights inside the carriages are also always on.
During the train's journey, the light inside the carriage changes with the external environment. For example, when passing the shaded side of a mountain, the outdoor light is relatively dim, whereas in areas with direct sunlight, the light is rather dazzling, so keeping the interior lighting system on at all times can help passengers better adapt to the light changes brought about by different outdoor lighting conditions, providing passengers with a more comfortable travelling environment.
Chinese Mainland media reports specifically mention the advanced Fuxing bullet train, stating that it has multiple lighting control modes, and the carriage lighting will automatically adjust according to outdoor conditions.
Finally, one more point: in China, not only are the headlights of high-speed trains always on when they are running, but the same is also true for conventional-speed railways, and you can try to pay attention to this the next time.
Read more: Why are there so few overnight high-speed trains in China?