Vehicles keep to the right-hand side of the road in Portugal. Often road names and numbers are not used in the countryside. Do not hesitate to ask the hospitable Portuguese who will be happy to point you in the right direction. Blue signs are used for villages or towns, green signs are usually used for highways and brown signs are used for other places of interest.
Circles or roundabouts, are more common than stoplights at intersections in Portugal. Right of way at these circles usually goes to the cars which have already entered the circle. When you come into a circle and don't know which exit to take out of it, consider going around until you find the sign for the town you want.
The speed limit on a highway is 120km. It is a toll road system and you can pay with cash. Keep in mind that Portuguese can be fast so, do not hesitate to slow down and let the impatient driver behind you pass.
While driving in Portugal, alcohol tolerance is zero!