Portugal used to have one of the highest accident rates in western Europe, but this has consistently improved as more and more money is spent improving the quality of the roads.
Roads in Portugal
A lot of money has been spent on building new roads in Portugal over the last 10 years. The main routes across the country, and around the major urban areas are of a good standard. Some are tolls roads, and are of reasonable value. However some of the the existing older roads are still in poor condition. In some areas where tourism is not at a high level, such as the Alentejo, minor roads continue to be of a low quality. If you drive with care, and take your time you should have no problems.