SPANISH ROAD SIGNS
Can anybody tell me please what the following road sign means. It is a square white sign with a picture of two cars (similar to the no overtaking sign) with diagonal lines through it. I came across this sign on several occasions when driving on country roads when after leaving a built up area or after a speed restriction sign and I'm not sure if it means that you can revert to the speed limit for that road or not. I was sticking to the last speed limit sign which had been 70 km/h and several cars overtook me and they didn't look too happy at the speed that I was doing. Whilst not wanting to get booked for speeding I'm also not wanting to get booked for the Spanish equivalent of careless driving.
Anyone that can help it would be much appreciated.