The A31 forms the main road along the peninsula at the SW end of the Isle of Man.
Descending to the end of the A31
The route starts at a TOTSO fork junction on the A5 at the head of the Bay ny Carrickey and heads west along Beach Road, briefly continuing along the shore before kinking inland. There are houses along the road from the start, enjoying the views across the bay, and the route is soon skirting the northern edge of Port St Mary. At a crossroads, it has to give way to the road leading into the village and harbour, which is the A29 to the north, and the B18 to the south. Now following Plantation Road, the route curves sharply to the right onto Howe Road, and soon leaves the town behind, although properties continue to be scattered along the roadside. The small village of The Howe is quickly passed through as the route climbs up Mull Hill.
Below the summit of the hill, a right fork leads into a large car park in an old quarry. This is for the picturesque heritage village of Cregneash, which lies just around the corner, and has been featured in films. The route summits at around 140m before beginning the long, winding descent westwards. The view ahead soon opens up, with the Calf of Man beyond the narrow channels either side of Kitterland. A short steep section the drops down to the car park and visitor centre at the end of the road, with traffic having to go into the car park to turn. A short walk along the coast path leads to Man's southernmost point.
As originally numbered, at some point between 1926 and 1929, the western part of the route, west of Port St Mary, was given the B31 number. However, by 1937 it is simultaneously listed as the B31 and, west of Cregneash, as the B36, a highly unusual situation. It had been renumbered and extended east to meet the former A7 as the A31 by 1963. It is therefore the only known example on the Isle of Man of a route being upgraded from a B to an A road without changing number.