Road sign S-5: Tunnel

What it means

«Indica el principio y eventualmente el nombre de un túnel, de un paso inferior o de un tramo de vía equiparado a túnel. […]» RD 465/2025, Annex I of the RGC (BOE-A-2025-12199), Spanish original.

It marks where the tunnel, underpass or equivalent stretch begins. It is an information sign: it tells you where it starts, and the bans inside are imposed by the regulation, not by the plate.

Where you meet it

You see it at the tunnel entrance. In the tunnel and on stretches with S-5, lighting is always compulsory (RGC art. 98.1), and turning round is not allowed (RGC art. 79.1).

What you must do

Switch on your lights, do not turn round and keep your distance: when not intending to overtake in a tunnel, the minimum gap is 100 m or 4 seconds. For vehicles with a maximum authorised mass over 3,500 kg, it is 150 m or 6 seconds (RGC art. 95.6). Overtaking depends on how many lanes your direction has: with only one, it is banned (RGC art. 87.1.d).

Details that count

The lights rule is read by the tunnel's illumination: if it is sufficiently lit, position and dipped lights suffice; if it is not, the road rule applies, unless there is a risk of dazzling (RGC arts. 99.1 and 101.1). A dark tunnel behaves like an unlit road (RGC arts. 100.1, 101.2 and 102).

What it is confused with

The classic confusion is to believe the tunnel sign prohibits something: it only informs. Inside, the cause of a stop separates two protocols: in a queue you stay, engine off and position lights on; if the vehicle breaks down or catches fire, you get out and go to the refuge (RGC art. 97.3).

Related signs

• R-300: Minimum following distance
• R-304: No U-turn
• R-305: No overtaking
• S-1: Motorway

Studied in topic 36: Tunnels, fog and snow.

Source: RGC arts. 79.1, 87.1.d, 95.6, 97.3, 98.1, 99.1, 100.1, 101.1, 101.2, 102; RGC Annex I, sign S-5 (RD 465/2025).