Looking north at the proposed new Grosvenor Road junction

From Monday, and for the three-year duration of the scheme, rush hour journeys could take 20 minutes longer.

During the first morning of work, traffic flowed quite well with no apparent major delays reported.

Northbound traffic cannot turn right onto the Grosvenor Road, while those going into Belfast must 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: "This morning, I believe people have taken heed of the information that was provided through the media over the past few days.

"They have adjusted their journey time. Quite clearly the morning peak hour has spread longer than normal and the serious congestion did not occur.

"The whole operation has been, in fact, quite a success."

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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.

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.

A spokesperson for the Department for Regional Development said motorists would be kept up-to-date with planned changes in traffic arrangements.

The work on the Westlink got under way on Monday

He said there would be alerts in newspapers, radio, television, the traffic information service (08457123321) and on the Road Service's Traffic Information and Control Centre website.

"The public can also receive an e-mail alert of significant traffic events on the M1/Westlink during construction," said the spokesperson.

"Register for this free service through www.roadsni.gov.uk/westlinktrafficalert."