Alderbury Junction was about half a mile from the village of Alderbury. Originally the West Moors line diverged as a double line, becoming single a short distance down the line. The layout was rearranged in 1943 to become a single trailing lead from the down (i.e. Salisbury direction) main line with crossover. An LSWR type 4 signal box was located in the apex of the junction. On the main line, to the west of the junction were Alderbury staff platforms. These were originally built to allow the transfer between West Moors and Southampton trains, but this appears to have stopped by 1881. After this the platforms were used for the families of railway staff, to pick up and drop off permanent way staff and in emergencies such as the failure of a train. Downton tunnel was to the north of Downton, on the descent from Whaddon to Breamore and was a small-bore tunnel, 107 yards long.