The Minister for Transport, Mr Brennan, yesterday turned the sod for an €80 million bypass.
The 11km road - part of the N15 linking Sligo and Lifford, Co Donegal - will take more than 9,000 vehicles a day away from the bottleneck towns, Bundoran and Ballyshannon, when it opens in autumn 2006.
Government and local authority experts reckon that by 2019 the number of cars, trucks and lorries bypassing the two towns will have risen to 20,000 a day.
The scheme includes construction of a 100-metre two-tiered bridge across the Erne river near the ESB's Cathaleen's Falls dam outside Ballyshannon. Pedestrians will use the lower level and vehicles the upper.
Mr Brennan said at the sod-turning ceremony: "There will be substantial journey-time savings, particularly at peak times. Most important of all, the new road will significantly improve safety, by replacing an existing route on which there have been a number of accidents, some very serious, in recent years."
The Minister said rapid progress was being made on a major road-building programme, which would be funded over the next five years with €7 billion provided by the State and €2 billion by private investors.
Meanwhile, an auctioneer complained that local people still haven't been paid agreed prices for land purchased for the road.
Mr Joe O'Neill, who acted for seven people who sold land so the Bundoran-Ballyshannon bypass could be built, said none of them had yet received any money from Donegal County Council.
Mr O'Neill said he understood several other people were owed an estimated several million euro by the council for property sold.
He realised the people would eventually get what they were owed, but they had made representations to him complaining they had not even been notified when they could expect their money.
He said: "In any normal business transaction you would expect that if a person buys your property he would pay for it before moving on to it."
Mr O'Neill, a member of Republican Sinn Féin, said he was not attempting to score political points, but highlighting the issue solely as an auctioneer representing his clients.
A spokesman for Donegal County Council said some people had been paid and in the case of others the process was under way, although not all would have been paid by the time work starts full-time on the road on July 30th.
He said it was normal in such schemes for some people not to receive their money before construction began, depending where on the route their property was located.