Motorists are being told to use the following diversions if they are travelling between Castle Douglas and Newton Stewart.
It follows an earlier crash on the A75 in which one person died and two others were injured.
The A75 is currently closed in both directions between the B796 (Gatehouse Of Fleet) and A755 (Girthon).
- Travelling East: Via A714, A77 and A713 to re-join A75 at Castle Douglas
- Travelling West: Via A713, A77 and A714 to re-join A75 at Newton Stewart
Police in Dumfries and Galloway are warning drivers not to use C class roads to try and shortcut a large diversion following a fatal crash on the A75 at Skyreburn.
Officers say drivers should follow the signposted diversions, which are around 77 miles long.
A force spokesman said: "In particular drivers of heavy goods vehicles should only use the diversion route as other C class roads are not suitable for that type of vehicle."
The A75 is closed in both directions after a fatal crash involving three cars.
Traffic is being diverted between Castle Douglas and Newton Stewart.
The diversion is around 77 miles long.
Police Scotland are currently dealing with a three car road crash on the A75 road at Skyreburn in Dumfries and Galloway. One man has been pronounced dead at the scene and others injured are presently being treated.
The roadway is completely closed and will remain so for some considerable time to allow a full crash scene investigation to take place. Diversions, which are lengthy, are being put in place. Motorists are asked to avoid this area if possible.
Police are renewing their appeal for witnesses after a 19-year-old boy died after being struck by a lorry on the A75 on Saturday night (17th August).
Kieran Currie, and two of his friends, were walking on the eastbound carriageway near to the top the entrance to Calgow farm, about a mile east of Newton Stewart, when he was hit by an eastbound passing lorry.
The lorry did not stop after the collision and has not been traced.
"This is a tragic set of circumstances which has left a young 19-year-old man dead.
"We are appealing to anyone who was using the A75 road in the Newton Stewart area at around 0240 hours on Saturday 17 August 2013 to get in touch with police through 101.
"The lorry which appears to have struck Kieran has yet to be traced, and it may well be that the driver of that vehicle is unaware that he has been in a collision.
"We are appealing for anyone who may have been in the area at that time to get in touch, and in particular, we want to hear from the drivers of all heavy goods vehicles who were on the A75 driving east around that time.
"Likewise we are keen to speak to the occupants of a small blue coloured car who stopped at the scene of the crash shortly after it happened and offered assistance.”
Police are appealing for witnesses after 19-year-old Keiran Currie died as a result of a road collision on the A75 on Saturday night (17th August).
The incident happened at 2.40am near to Calgow Farm, about one mile east of Newton Stewart.
Police are looking to speak to the people who stopped to offer help shortly after the accident.
They were travelling in a small blue car.
If you witnessed the accident or seen anyone walking in the area before 2.40am, please contact police on 101.
A nineteen year old man is in a serious condition at the Dumfries and Galloway Royal Infirmary after he was apparently hit by an eastbound lorry on the A75 a mile east of Newton Stewart at approximately 2:40am on Saturday 17th August.
Police believe that a number of vehicles will have been in the area around the time of the accident and are urging anyone who might have information about the accident to contact them. They say they have already spoken with a number of lorry drivers in relation to the accident.
Some drivers may have been slightly alarmed to see a huge model of comedian Jimmy Carr being transported up the A75 today.
The massive face was being moved from Preston to Dundrennan, in Dumfriesshire, in preparation for the annual Wickerman Festival on 26th and 27th July.
A multi-million pounds scheme to upgrade part of the A75 where a baby died has begun.
The road improvements are along a two and a quarter mile stretch between the Hardgrove crossroads and Carrutherstown.
The road is the main route to the port at Stranraer and is used by thousands of cars and lorries every day.
Matthew Taylor reports: