 During 1940, Centralised Train Control (CTC), which allowed direct control of signals and train movements by Train Control in Wellington, was progressively installed on the single line sections of track north of Tawa, replacing tablet working and allowing more efficient, flexible, and rapid control of train movements.CTC between Plimmerton and Paekakariki applied from 25 February 1940, Paremata to Plimmerton from 30 June, and Tawa to Porirua from 4 December 1940.On 24 July 1940, the line through Porirua, from Wellington to Paekakariki, was electrified and double track completed from Plimmerton to South Junction, just north of Muri railway station.