Motorists using Belfast's Westlink have been told to expect delays of up to 40 minutes as work on the multi-million pound road upgrade gets under way.
Looking north at the proposed new Grosvenor Road junction
From Monday, northbound traffic will be unable to turn right from the Westlink onto the Grosvenor Road.
Drivers heading into the city will have to exit either at the Divis Street or Broadway turn-offs.
Those travelling southbound will be unable to turn right towards the Royal Victoria Hospital.
Roy Spiers of the Roads Service said motorists should leave extra time for their journey.
"It will be difficult until motorists become familiar with the traffic arrangements that are in place," he said.
"I would encourage them to allow extra time for their journeys on Monday morning until they know what is actually happening and become familiar with their route."
The work, which will create three continuous lanes on the M1 and Westlink between Blacks Road and Divis Street junctions, is due to be completed in the spring of 2009.
The Westlink carries 65,000 motorists every day and is Northern Ireland's busiest road.
Two lanes will be maintained in both directions throughout the work from 0600 GMT until 2200 GMT on Monday to Saturday and from 1100 GMT on Sundays.