The air pollution is aggravated by developments that typically occur as countries become industrialized. Growing cities signify constructions of roads and buildings, industrializations, constant increase in traffic, expanding commercial activities, teeming population and growing consumers, widespread economic activity, expanding transportation networks and high levels of energy consumption. The high influx of population in urban areas, increase in consumption and unplanned urban and industrial growth has led to serious air pollution threats.

Currently, in India, air pollution is prevalent extensively in urban areas where vehicles are the major contributors. Establishment of several heavy industries and thermal power plants also add to pollution levels tremendously. Vehicle emissions are of particular concern since these are ground level pollutants and thus have profound impact on the general population. Also, vehicles contribute significantly to the total air pollution load in many urban areas.

All motor vehicles release pollutants into the air, mostly through the exhaust fumes that come out of the tailpipe when the engine operates.

It would shock anyone to realize that:

• More than 99.4 per cent of all pollutant gases are invisible

• Cars release emissions even when it is standing still

• Other fumes from petrol and lubricants evaporate into the air

Pollutants produced by vehicle exhausts include carbon monoxide, hydrocarbons, nitrogen oxides, particles, volatile organic compounds and sulfur dioxide. Hydrocarbons and nitrogen oxides react with sunlight and warm temperatures to form ground-level ozone. Ground-level ozone, a main ingredient in smog, can cause upper respiratory problems and lung damage.

Motor vehicles are responsible for about 70 per cent of air pollution. Unless we all start reducing car use and motor vehicle pollution, this level is set to increase dramatically. An average car creates almost six tones of pollutants each year. That's approximately equivalent to the weight of seven small cars.

Despite this, we are fortunate that current air quality is relatively good, but if the fast deteriorating situation is not brought under control conditions will not remain the same in the near future.

Releasing some emissions (and causing some air pollution) is an unavoidable by-product of using a motor vehicle. However, there are simple steps you can take to make sure your vehicle's emission levels are as low as possible.

• 16 per cent less tailpipe hydrocarbon emissions

• 26 per cent less tailpipe carbon monoxide emissions

• 9 per cent less nitrogen oxides emissions

Between 1951 and 1991, the urban population has tripled, from 62.4 million to 217.6 million, and its proportion has increased from 17.3% to 25.7%. Nearly two-thirds of the urban population is concentrated in 317 class I cities (population of over 100 000), half of which lives in 23 metropolitan areas with populations exceeding 1 million. The number of urban agglomerations/cities with populations of over a million has increased from 5 in 1951 to 9 in 1971 and 23 in 1991.

The number of motor vehicles has increased from 0.3 million in 1951 to 37.2 million in 1997 (MoST 2000). Out of these, 32% are concentrated in 23 metropolitan cities. Delhi

itself accounts for about 8% of the total registered vehicles and has more registered vehicles than those in the other three metros (Mumbai, Calcutta, and Chennai) taken together.

At the all-India level, the percentage of two-wheeled vehicles in the total number of

motor vehicles increased from 9% in 1951 to 69% in 1997, and the share of buses declined from 11% to 1.3% during the same period (MoST 2000).

This clearly points to a tremendous increase in the share of personal transport vehicles. In 1997, personal transport vehicles (two-wheeled vehicles and cars only) constituted 78.5% of the total number of registered vehicles.

Road-based passenger transport has recorded very high growth in recent years especially since 1980-81. It is estimated that the roads accounted for 44.8 billion-passenger kilometer (PKM) in 1951, which has since grown, to 2,515 billion PKM in 1996.

The freight traffic handled by road in 1996 was about 720 billion tonne kilometer (TKM) which has increased from 12.1 TKM in 1951 (MoST 1996). In contrast, the total road network has increased only 8 times from 0.4 million kms in 1950-51 to 3.3 million kms in 1995-96. The slow growth of road infrastructure and high growth of transport performance and number of vehicles all imply that Indian roads are reaching a saturation point in utilizing the existing capacities. The consumption of gasoline and HSD has grown more than 3 times during the period 1980- 1997. While the consumption of gasoline and HSD were 1,522 and 9,050 thousand tones in 1980-81, it increased to 4,955 and 30,357 thousand tonnes in 1996-97, respectively.