I can tell you that traffic was horrible on Lisbons exits last night, and yes, it is a "car based problem". So much that the police traffic brigade almost always has extra measures prepared for such occasions.

A suggestion to end bridges was made some time ago, by deslocation the day off from the official day to the next friday or previous monday. As a sort of compensation it was also suggested that when such days happen on a weekend they could be dilocated for friday or monday, also.

This turned out to be unpopular, especially because of religious holidays. I guess people don't care of they celebrate the Republic on the 6th of october instead of the 5th. But Xmas on the 26 or Mardi Gras on a monday? Not so cool...