Just like driving in most countries, Portugal driving rules are very similar to others in Western Europe. In the past few years Portuguese traffic cops are not as lenient as they once were. So be wise and follow the rules of the road as you would not like to face fines, or even worse be involved in an accident.
It is obligatory to carry the following items in the car at all times. Not having any of them can result in a fine if pulled over by the police. Fines vary, but can go up to a few thousands Euros.