Roads officials hope the opening of the £17 million Dunragit bypass on the A75 between Stranraer and Dumfries will end Challoch bridge’s unenviable record of being hit more than 100 times in the last ten years.
Incidents, which have involved European lorry drivers heading to or from Northern Ireland via the Cairnryan ferry port, have shut both the road and the Glasgow-Stranraer rail line for hours.
It is estimated such collisions cost £700,000 a year in damage and delays.
The Scottish Government’s Transport Scotland agency said traffic would start using the three-mile bypass some two months early.
Project manager John Quail said: “This early switch of traffic onto the new bypass will bring immediate benefits by taking trunk road traffic away from the village and the Challoch rail overbridge, thereby reducing the likelihood of bridge strikes, which cause lengthy diversions and delays to journey times.
“On completion and when fully open [this summer], the bypass will improve journey time reliability, reduce driver frustration and vehicle platoons.”