There could be rush-hour misery for commuters in and around Douglas this evening.
Police are warning the late road closures for tonight's Superstock race could cause gridlock in the Island's capital.
The evening race has been added to today's schedule after Saturday's racing was postponed.
Police are urging people who have to travel into Douglas to consider alternative routes or organise a car-share.
The mountain road is due to close at 11am, and the rest of the course 30 minutes later.
Crossing points, or 'access corridors' will be open to vehicles for an hour, from 5pm, to help commuters get home, but police are stressing the circuit will not reopen until all the racing has finished.
Yesterday afternoon, Manx Radio asked shoppers in Strand Street for their views on the extra disruption (play audio file):
It's hoped the roads will start to reopen from St Ninian's from about 8pm, and the rest of the course, apart from the mountain section, should be back to normal in about half an hour.
It's hoped traffic will be back on the mountain, between Ramsey Hairpin and Creg-ny-Baa, by 9.30pm.