the Caledonian Railway began an extensive reconstruction of the station. The existing island platform buildings were remodelled with new windows and doors and the exterior was given a dressed stonework finish. The accommodation comprised ladies’ and gentlemen's waiting rooms, a telegraph office, a tea room and offices for the station staff. The buildings extended to , with steel and glass platform canopies which extended beyond the length of the platform building. The platforms were raised in height and extended in length to around . The constricted layout of only one set of up and down through lines was expanded with the provision of loop lines for both up and down trains to allow non-stop trains to bypass any trains stopped at the station. The improvements were prepared under the direction of W.A. Paterson, the engineer-in-chief of the company. The contract for the reconstruction was won by John Shirlaw of Carluke. The reconstruction cost £22,391 (). The London, Midland and Scottish Railway constructed an experimental locomotive. LMS 6399 Fury. On a test run from Glasgow to Carstairs scheduled for 10 February 1930 it was approaching Carstairs station at slow speed, when one of the ultra-high-pressure tubes burst and the escaping steam ejected the coal fire through the fire-hole door, killing Lewis Schofield of the Superheater Company. Electrification The route through the station was electrified in the 1974 electrification scheme that covered the West Coast Main Line between Weaver Junction and . As part of this the station was re-signalled. The critical point was the connection from Edinburgh on a minimum radius curve to provide a connection into the Down platform whilst avoiding the installation of a diamond crossing. The provision of superelevation through the Up platform for 90 mph running required deep ballasting; this required the platform to be raised. The original station buildings were being retained, and continuous railings were provided to prevent passengers accidentally falling down from one level to the other. This height difference has now been removed as the original station buildings were demolished and replaced with a more modern alternative and the entire platform was levelled off. The only remnant of the original station buildings was the integral footbridge, now adapted as a stand-alone structure. The route to Edinburgh was not part of the 1970s scheme; however, it was included as part of the late 1980s ECML scheme, with electric services starting to use the line