When driving below 40 km/h on a road outside a built-up area that is not sufficiently lit, you must have the following lights on:

Correct answer: low beams, at least.

At 40 km/h or less on a poorly lit road outside a built-up area, high beams are no longer required. You must use at least your low beams, along with your position lights, and you may use high beams if they do not blind anyone with glare. Position lights alone are not enough.

Real Decreto 1428/2003, de 21 de noviembre, por el que se aprueba el Reglamento General de Circulación · Real Decreto 1428/2003, de 21 de noviembre, por el que se aprueba el Reglamento General de Circulación