What are the three main functions of a vehicle's lighting system?

To see, to be seen, and to signal A vehicle's lighting fulfils three essential functions: to see the road and surroundings, to be seen by others, and to signal the driver's intentions, such as turning, braking, or reversing.

When lighting is mandatory and the vehicle is moving, which lights must be switched on as a minimum?

At least one light to see and one to be seen Whenever lighting is mandatory and the vehicle is moving, it must have at least one light to see and one light to be seen switched on, ensuring the safety of the driver and others.

During which period of the day is the use of lighting mandatory?

Between sunset and sunrise Lighting is mandatory between sunset and sunrise, since at night natural visibility is insufficient to drive safely.

When is lighting considered insufficient for driving?

When you cannot read a number plate at 10 m nor distinguish a dark vehicle at 50 m Lighting is considered insufficient when you cannot read a number plate from 10 metres or distinguish a dark-coloured vehicle from 50 metres away.

Is it mandatory to switch on the lighting when passing through a tunnel?

Yes, whenever driving through a tunnel or underpass In tunnels, underpasses, and stretches signposted as such it is mandatory to switch on the lighting, since natural light suddenly disappears and visibility is reduced.

Lighting and Optical Signals

Study all Lighting and Optical Signals questions for the Spanish DGT theory test.

Reviewed on 7 Oct 2026

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Frequently asked questions

What are the three main functions of a vehicle's lighting system?: To see, to be seen, and to signal A vehicle's lighting fulfils three essential functions: to see the road and surroundings, to be seen by others, and to signal the driver's intentions, such as turning, braking, or reversing.
When lighting is mandatory and the vehicle is moving, which lights must be switched on as a minimum?: At least one light to see and one to be seen Whenever lighting is mandatory and the vehicle is moving, it must have at least one light to see and one light to be seen switched on, ensuring the safety of the driver and others.
During which period of the day is the use of lighting mandatory?: Between sunset and sunrise Lighting is mandatory between sunset and sunrise, since at night natural visibility is insufficient to drive safely.
When is lighting considered insufficient for driving?: When you cannot read a number plate at 10 m nor distinguish a dark vehicle at 50 m Lighting is considered insufficient when you cannot read a number plate from 10 metres or distinguish a dark-coloured vehicle from 50 metres away.
Is it mandatory to switch on the lighting when passing through a tunnel?: Yes, whenever driving through a tunnel or underpass In tunnels, underpasses, and stretches signposted as such it is mandatory to switch on the lighting, since natural light suddenly disappears and visibility is reduced.