The left lane is open to traffic in the opposite direction from usual; what is the maximum speed at which vehicles traveling in the right lane may drive?

Correct answer: 80 km/h.

If the left lane is opened for traffic traveling in the opposite direction from normal and only the right lane remains in your direction, you must drive in that lane at a maximum of 80 km/h and a minimum of 60 km/h, unless a sign sets a lower limit. The road's 120 km/h limit does not apply while this situation lasts; normal limits apply again only if two or more lanes remain in your direction.

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