Hitching is never entirely safe, and we don’t recommend it. Travellers who hitch should understand that they are taking a small but potentially serious risk. People who do choose to hitch will be safer if they travel in pairs and let someone know where they are planning to go.
Hitching is illegal on autopistas and autovías, and difficult on other major highways. If you must, choose a spot where cars can safely stop before highway slipways, or use minor roads. The going can be slow on the latter, as the traffic is often light.