Tunnel Driving Rules in Spain

The main tunnel driving rules in Spain are simple: turn on your dipped headlights before you enter, however short the tunnel, keep at least 100 metres or 4 seconds behind the car in front, and do not overtake unless there are two or more lanes in your direction. If you break down inside, get out of the tunnel if you can; if you cannot, stop as far to the right as possible, put on your hazards, and signal for help. These rules appear on the DGT theory test, and they matter in real life because a tunnel gives you no hard shoulder and no easy escape.

What lights do you need before entering a tunnel?

You must switch on your dipped headlights (luz de cruce) before you enter any tunnel, no matter how short it looks. Do it while you are still in daylight, before the entrance, not once you are already inside. A tunnel changes the light level suddenly, and your eyes take a moment to adjust, so having your lights on early makes you visible to everyone around you.

Dipped headlights are the low beam, the everyday setting you use at night in town. You do not need main beam (high beam) in a tunnel, and you should not use front or rear fog lights unless there is genuine smoke or reduced visibility. The point is to be seen, not to dazzle the drivers ahead of you or coming towards you in a two-way tunnel.

Leave your lights on until you are fully back out in the open. A common mistake is switching them off too early, near the exit, when there is still traffic behind you in the dark. Keep them on all the way through and a little beyond. On the DGT test, the safe answer is almost always "dipped headlights, on before entering".

How much distance should you keep inside a tunnel?

Inside a tunnel you should keep a bigger gap than usual: at least 100 metres or 4 seconds behind the vehicle in front for a car. If your vehicle weighs more than 3,500 kg, the recommended gap grows to 150 metres or 6 seconds. These figures are illustrative rather than something a police officer measures with a tape, but the idea is real: more space means more time to react.

Why the extra room? A tunnel has no hard shoulder to swerve onto, poorer light, and often a wall right beside you. If the car ahead brakes hard or stops because of a jam or an incident, you want enough distance to stop calmly rather than pile in. The time method is easy to use: pick a fixed point on the wall, and if you reach it less than 4 seconds after the car ahead passed it, you are too close.

If traffic stops completely inside the tunnel, keep your distance from the car in front even when stationary, and stay alert. For the full method and how to judge gaps by seconds, see our guide to safe following distance in Spain.

Can you overtake inside a tunnel?

No, you cannot overtake inside a tunnel unless there are two or more lanes running in your direction. In a standard single-lane tunnel, overtaking is prohibited, and this is a frequent exam question. Crossing into the oncoming lane in a confined space with limited visibility is exactly the kind of manoeuvre the rules are designed to stop.

Where a tunnel does have two or more lanes for your direction of travel, overtaking is allowed, using the normal rules: overtake on the left, signal, and return to your lane when it is safe. Even then, stay cautious. Tunnels can be noisy, poorly lit compared with the open road, and drivers around you may be uneasy, so leave plenty of margin.

Overtaking bans apply in several other places too, such as blind bends, crests, pedestrian crossings and level crossings. The tunnel rule fits the same logic: no overtaking where you cannot clearly see far enough ahead to do it safely.

What should you do if you break down in a tunnel?

If your vehicle breaks down inside a tunnel, your first choice is to keep going and leave the tunnel if the vehicle can still move. Getting out into the open is always safer than stopping in a confined space. If you truly cannot exit, use a lay-by or emergency bay if one is nearby, and otherwise stop as far to the right as you can, keeping the traffic lane clear.

Once stopped, follow these steps in order:

• Switch on your hazard warning lights and your position (side) lights so you are visible.
• Turn off the engine.
• Call for help using the nearest SOS emergency post, which connects you to the tunnel control centre.
• Put on a high-visibility vest before you get out of the vehicle.
• Move to a refuge or emergency exit and wait there, not next to your car in the traffic lane.

The safest place is behind a barrier or in a marked refuge, away from moving traffic. Do not try to fix the car in the lane, and do not stand between your vehicle and oncoming traffic. Signalling through the SOS post is important because the control centre can warn other drivers, slow the traffic, and send help straight to your location.

What does the tunnel sign (S-5) look like?

A tunnel ahead is marked by sign S-5, a blue square showing a white tunnel arch symbol. When you see it, it is your prompt to check your headlights are on, ease off the accelerator if needed, and open up the gap to the vehicle in front. The sign is informative rather than a prohibition, but it is telling you the road conditions are about to change.

Spanish signs use letter codes, and the S series covers "indicacion" or information signs that give you useful details rather than orders. Learning these codes is one of the trickier parts of the theory exam for English speakers, because the letters do not map onto the systems used in other countries. You can drill signs and their meanings on our practice topics page, and the wider licence journey is covered in our pillar guide to the DGT theory test in English.

Tunnel lighting also connects to the general rules on when to use each type of light. If you are unsure about dipped beam, fog lights and main beam, read our guide to headlight rules in Spain.

Frequently asked questions

Do I need headlights in a very short tunnel?

Yes. You must turn on dipped headlights before entering any tunnel, however short. There is no minimum length that lets you skip them, and it is a common trap on the DGT theory test.

How far behind the car in front should I stay in a tunnel?

At least 100 metres or 4 seconds for a car. For a vehicle over 3,500 kg, the recommended gap is 150 metres or 6 seconds. The figures are guides, so give yourself extra room when in doubt.

Is overtaking ever allowed in a tunnel?

Only when the tunnel has two or more lanes in your direction of travel. In a single-lane tunnel, overtaking is prohibited. If in doubt, do not overtake and wait until you are out.

Are emergency triangles still used inside tunnels?

Since 1 January 2026, the connected V-16 light replaced triangles as the only valid breakdown signal in Spain. Inside a tunnel the priority is to reach safety and use the SOS post, not to place any device in the traffic lane.

What is sign S-5?

Sign S-5 is a blue information sign with a white tunnel arch symbol that warns of a tunnel ahead. Treat it as a reminder to switch on your lights and increase your following distance before you enter.

Sources

• Reglamento General de Circulacion (Real Decreto 1428/2003).

Last updated: August 2026.