Six locations - Brampton, Toronto Port Union, Ottawa Canotek, Kitchener, North Bay and Thunder Bay are open.
Only partial services will be offered: written tests for all classes of licences, road test for commercially classified licences and out-of-province/out-of-country licence exchanges. They will not be performing G2 or G tests.
Union members - on strike since August - rejected DriveTest's latest offer with a vote of 78 per cent on Wednesday.
There is now a backlog of 300,000 tests and re-certifications in Ontario.
With files from The Canadian Press