By David Willey in Rome

Millions of Italians living in the Milan area went without their cars on Sunday in an experiment aimed at reducing atmospheric pollution levels.

For 17 days, smog and suspended particles in the air have posed a health risk to the citizens of Milan. The city-wide car - put in place at eight o'clock on Sunday morning - was top of the national news.

Only electric cars, city buses and essential services such as the police are allowed on the streets until eight in the evening.

The reaction so far has been fairly positive. No one likes to suffocate for days on end under a blanket of pollution. One motorist said he had two cars but was quite happy to leave them both at home on a Sunday.

Another motorist who appeared on horseback in the city centre said he and his friends had clubbed together to buy a horse.

Traffic police levied on-the-spot fines of $60 on private motorists who broke the car ban.

The car ban was in force not only in the centre of Italy's leading industrial city but also in the suburbs and in other nearby towns, such as the lakeside resorts of Lecco and Como.

Francesco Ferrante, the president of Italy's leading environmental association, has his doubts, however, as to whether Sunday's car ban, due to be extended to other Italian cities next month, can ever solve the basic problem - that there are too many cars.

"I do think that for big cities like London, maybe for Rome, like Paris, the traffic problem is something that cannot be solved at all.

"So we are too many; there are too many cars; and our cities (have) not been built for cars. You can obviously diminish the problem, but you cannot solve it completely."

From Sunday night, the centre of Milan will once more fill with traffic. Only on Monday morning shall we know just how much pollution levels have fallen.