Much of the pressure has come from the land where the car is king-california. The United States has no public transport to speak of (the major car-makers actively contributed to its destruction) so the car is the average Amerrican's only practical means of daily transport. But some US cities, Lost Angeles in particular, are paying a high price for this over-reliance.LA's famous smogs - trapped by the natural "bowl" of the nearby mountains - are the result of reactions between the chemicals which come from the city's millions of car exhausts.