Road signs are, for the most part, made to be understood internationally and in Spain most of them are easy to decipher. Nevertheless, here’s a brief summary of the basics and some signs you may find confusing.
First, examples of warnings of danger ahead:
Red upward triangles on white: Warning 
Strong crosswinds 
Obstruction ahead 
Low visibility 
Self-explanatory 
Don’t drive off the dock.
Then, the prohibitions:
Red circle on white: Prohibitions 
No pedestrians allowed 
Maximum speed, easy. 
No passing, of course. 
No cars or bikes allowed. 
Don’t blow you top off.
No parking. 
No parking AND no stopping. 
Vado = Driveway.
Blue ones can be tricky as they vary from “Obligatory/compulsory” to “Reserved for” to “Minimum” to “Between”.
Must go this way. 
Must go that way. 
🙂
Cars only, no morotcycles 
Lane reserved for motorcycles 
Lane reserved for bikes
Compulsory minimum speed. 
Must use chains. 
Turn lights on.
Then, there are the crossed-out signs that mean “End of” whatever they are crossing out. Here are some examples:
End of speed limit, which don’t usually inform of the new one. 
End of residential area 
End of highway 
End of parking restriction 
End of town or city. 
End of tunnel. In case you missed it.
Other useful signs to know:
Suggested speed. 
Suggested range of speed. 
Rest area. Note: no WC in these stops. 
Distance to next exit. 
Upon exiting a tunnel, so you remember to turn off your lights if it’s daytime. 
You can’t pull a U-ie, go this way instead.
Every other sign you come across will be easy to decipher if you give it a little thought.
In Driving in Spain you will find information about the different highway and road signs.
