Every vehicle must be tested and approved for it to be eligible for its next revenue license, Patali Champika Ranawaka, minister of environment and natural resources, said.
Owners of vehicles that fail the test will be given time to repair the engines and make necessary adjustments to re-apply for a new certificate.
Vehicles that are beyond repair will have to be converted to liquid petroleum gas and owners will be given an interest free loan to complete the conversion, Ranawaka also said.
"It has been planned to launch the loan scheme by next year."
The tests will check the opacity or the 'K' value of the tail pipe exhaust emissions from diesel engines. The K level should be less than eight.
In petrol engines, the Carbon Monoxide and level of un-burnt hydro carbons in exhaust fumes will be tested when issuing the VET certificate, Anura V