The Department of Infrastructure says a section of the TT course will close for two weeks from Monday.
Drainage and resurfacing works means Creg Willey's Hill will shut between Ballig Bridge and Cronk Y Voddy from 9.30am on Monday, March 17.
The DOI says TT organiser ACU Events described the work as essential for this year's racing - because water could seep onto the road and create a race hazard.
Traffic will be diverted via Poortown Road.
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