Road sign S-51a: Lane reserved for specific types of vehicle

What it means

«Indica un carril destinado exclusivamente a la circulación de cierto o ciertos tipos de vehículos determinados (autobuses, motocicletas, vehículos de tres ruedas asimilados a motocicletas, taxis, ciclos, etc.). […]» RD 465/2025, Annex I of the RGC (BOE-A-2025-12199), Spanish original.

It reserves a lane, exclusively, for certain types of vehicle: buses, motorcycles, three-wheelers treated as motorcycles, taxis, cycles and the like. The sign's pictogram says which.

Where you meet it

You see it on a road with a separate lane for those vehicles, for instance on a busy urban street. It belongs to the lane signs (RGC art. 146.2.b). It is an information sign of the lane family, not a no-entry ban.

What you must do

If your vehicle does not appear in the pictogram, do not drive in that lane: the pictogram says who may use it, so check it before entering.

Details that count

Tell a reserved lane from a reserved place. S-51a is about driving in a lane that is exclusively for certain types of vehicle; S-18, «Place reserved for taxis», shows the place reserved for stopping and parking of free taxis in service, with a number giving the total of reserved spaces (RD 465/2025 catalogue). One is about driving, the other about stopping and parking. In the exam, what is asked is who may use the lane, and the answer is in the pictogram.

What it is confused with

It is confused with S-3, «Road reserved for motor vehicles». Both speak of something «reserved», but S-3 refers to a whole road and to cars; S-51a to one lane and to the types the pictogram shows. Do not mistake it for a no-entry ban: S-51a is an information sign.

Related signs

• S-3: Road reserved for motor vehicles
• R-101: No entry
• S-17: Parking

Studied in topic 10: Vertical road signs.

Source: RGC art. 146.2.b; RGC Annex I, sign S-51a (RD 465/2025).