Changes had been due to end this month
The reversed one-way system on Finch Road in Douglas is to remain in place until December.
The Department of Infrastructure is extending the changes, which had been due to end this month, having initially come into force on 5 January.
Traffic will only be able to travel in a northerly direction along the road until 14 December while the current phase of Douglas promenade works continue.
Parking on Prospect Hill between Athol Street and Hill Street will remain suspended.
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