Rigid measures are being imposed to ensure roads around the TT course open between 5 and 6pm throughout race week.
That's with the exception of the one-way system between Ramsey Hairpin and Creg ny Baa.
The new rule announced by the Department of Infrastructure on Friday, will apply to every race day or postponed race day but not Senior Race Day.
In the past, race organisers have had flexibility over how long to open roads and crossing points - but now, it will be compulsory to re open roads for the full hour.
The change follows a flood of complaints from motorists last year, when delays to the TT schedule meant some roads and crossing points only opened for a short time, creating traffic gridlock.
Director of Highways Richard Pearson