Registrar of Motor Traffic B Wijeratne says there about 1.9 million vehicles on the roads now though his department has registered about three million vehicles so far.
By the end of 2008, the vehicle population is expected to reach 2.4 million.
The country's three-wheeler taxis which use two stroke engines have become a key cause of atmospheric pollution in the city. Last year out of 300,000 vehicles registered in the island 64,000 were three wheelers.
Taking a cue from India the county has announced a ban on the import of two-stroke engine three wheelers and motorcycles. However the move is resisted by three wheeler owners who are politically powerful.
Unlike cars which use four-stroke internal combustion engines where only petrol or diesel is burnt, two stroke engines also burn engine oil which is mixed with petrol, making them a major health hazard.
“There has been an alarming increase in respiratory disorders particularly among children in the country for which the primary cause is unchecked vehicle exhaust emissions,” Ruwan Wijemuni, deputy chief medical officer of the Colombo Municipal Council said.
Tests have found that air quality of the ground floor of urban schools was much worse than that of rural schools.
Environmental minister Champika Ranawaka says environmental laws would be tightened next year.
“The government has made a decision to strengthen all the rules and regulations that deal with conserving the environment,” he said at a ceremony in Colombo to launch an emission testing program.
"We have sought advice from the supreme court also regarding this."
Emission certificates would be made compulsory from April 2008 for all vehicles. The certificate would have to be submitted to get the annual revenue license.
Two firms, Clean Co. (Pvt.) Limited and Laugfs Holdings Limited, have been officially authorized to conduct the tests, through 32 permanent and 80 mobile testing stations.
Transport minister Dulles Allahapperuma says making combustion cleaner would cut down fuel use by improving the efficiency of vehicle engines.
The environmental ministry estimates that a one percent reduction in emissions would save a billion rupees of fuel.
Sri Lanka's government policies have contributed to environment pollution and discouraged the use of cleaner fuels and smaller vehicles.
Diesel is heavily subsidized compared to petrol, despite petrol being a cleaner fuel. This has discouraged its use. Diesel vehicles in general are heavier than petrol ones.
Most politicians use heavy, diesel guzzling super luxury jeeps imported duty free. Earlier this year government officials were provisionally given a chance to import more than 20,000 tax slashed cars.
In the 1990's people stopped buying petrol cars and switched to heavier, diesel vans, as petrol was priced at 50 rupees a litre and diesel at only 13 rupees.
Starting from 2002 the gap between diesel and petrol was narrowed, and leaded petrol was eliminated. But in 2007 the gap between diesel and petrol has started to widen again.Sri Lanka also started to heavily subsidize fuel from 2004 sending the wrong price signals to the economy.