At present, 3 300 000 cars are registered in the Czech Republic. Out of this, 703 000 cars are registered in Prague, 589 000 of these being passenger cars. The current situation is characterised by these features:

• a marked rise in the number of cars over the past 6 years
• a relatively large proportion of cars older than 10 or even 15 years
• poor ability of the road network both in and outside the cities to accommodate the enormous increase in traffic intensity
• increase in overall emissions
• low possibility to reduce the emissions from the obsolete vehicle pool

For illustration let us present some data for Prague:
Whereas in the eighties the number of cars in Prague rose annually by about 6 000 cars, in the period 1990-1996 the average yearly rise was 42 000 and during 1996 it was 53 000 cars. The city centre, where our school is also located, is choked with cars practically all day through. The enclosed map of Prague with the mean yearly concentrations of nitrogen oxides documents the situation. Car traffic is the largest anthropogenic source of NO_x. When evaluating the pollution situation in Prague it becomes apparent that the concentration of CO, SO₂ and flue dust (thanks to replacement of solid fossil fuels by natural gas) is being successfully reduced whereas NO_x concentrations moderately rise.

Still, the rise in total traffic-generated emissions in Prague does not correspond to the rise in the number of cars because a relatively fast renewal of the vehicle fleet takes place, especially for passenger cars, which are equipped with three-way catalytic converters. This renewal is illustrated by the enclosed graph showing the increase in the consumption of unleaded gasoline Natural (see page 23).

Air pollution by car emissions has an adverse impact on the health condition of the populace. Nitrogen oxides and sulphur oxide damage the respiratory tract, carbon monoxide blocks oxygen transfer by haemoglobin, many hydrocarbons are documented carcinogens, heavy metals damage the liver, nerve tissue, etc. In addition, these harmful substances undergo in the atmosphere photochemical and chemical conversions that give rise to other noxious substances, e.g. ozone, aldehydes, HNO₃ or H₂SO₄. Especially dangerous is ozone, which is formed in large quantities in inversion spells, under a simultaneous action of sunlight, in areas with high traffic intensity. A special type of smog called the photo-smog or Los Angeles type smog arises at these places.

If we do not want to give up our current life style, it is therefore necessary to reduce the emissions as much as possible. This effort requires a very close co-operation of the automotive and the chemical industries.
 

Yearly consumption of unleaded gasoline in per cent of total gasoline consumption for the period 1990-1997