What does this sign mean?
En español: ¿Qué significa esta señal?
Why this is the correct answer
Indicates the kilometre point on a conventional road, whose identification appears at the top on a background colour corresponding to the road network to which it belongs: RED: Road in the State network (see sign S-420). ORANGE: First-level regional road (see sign S-430). GREEN: Second-level regional road (see sign S-440). YELLOW: Third-level regional road (see sign S-450).