Tens of thousands of citizens in Paris, Geneva, Brussels, Rome, and some 150 other European cities left their automobiles at home yesterday to observe a car-free day, the second annual one in France and first in Italy. Enviros hope the day caused drivers to think about smog and their role in creating it. A French Environment Ministry poll said that 64 percent of the French believe traffic levels have become unbearable. Still, some shopkeepers in Paris complained about the ban, fearing it would keep people out of the city and away from their shops. In Rome, the car-free day had mixed results; just a handful of streets were closed by the city government to mark the day and traffic was nearly as congested as usual in most of the city. Rome is preparing for a permanent traffic block; every Wednesday beginning October 6, cars and bikes will not be permitted in the center of the city.