The Mountain Road becomes one-way for the duration of TT fortnight from today (Saturday).
The system, from Ramsey Hairpin to Creg-ny-Baa, was first introduced four years ago to improve safety and reduce the likelihood of head-on collisions on the mountain section of the TT course during the busy period.
The road is closing at 10am for cones and signs to be put out.
It will re-open later with traffic travelling in the direction of the course only, until Monday, June the 13th.
As usual, police are stressing that, despite the one-way system, it is still illegal to cross solid white lines, and the route will be policed around the clock.