The Department of Infrastructure says the Mountain Road is now closed until no later than midday, Tuesday, June 16
It's so workers can remove the two-way traffic reminder signs which were used for TT.
The signs were there to warn people after the one-way system was removed.
The closure is in place between Barrule Park in Ramsey and the Creg Ny Baa.
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June sitting of Tynwald to take place today