Are there any special requirements for driving or  hiring a car in Portugal?
In Portugal, one drives on the right with overtaking on the left, you can be fined more than 1,000 Euros if you pass a driver on the right. On the motorways there are three lanes with the middle one being for overtaking. At night in rural areas look out for horse drawn carts. When a tram stops and there are no island for passengers to disembark at, drivers must give way to them. Avoiding rush hour traffic in the cities is to be advised.
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It is safest to drive defensively in Portugal, which has one of the less impressive driving safety records in Europe. You can find interactive online maps of the country at http://www.travelportal.info/western-europe/portugal/maps.