As part of the Plimmerton to Paekakariki duplication, a Westinghouse three-wire (two feed and one return) Centralised Train Control (CTC) system was installed in 1940; to control trains from Wellington. It was the first CTC system in New Zealand and the first outside the United States of America. This avoided the need for two new signal boxes at the North and South junctions and the need with "tablet" working to continuously man five stations (Tawa, Porirua, Paremata, Plimmerton and Pukerua Bay; with 3 or 4 tablet porters at each station); so requiring 19 men for traffic working. CTC working applied between Paekakariki and Plimmerton on 25 February, Plimmerton and Paremata on 30 June and Tawa to Porirua on 4 December 1940; giving full traffic control from Wellington to Paekakariki (as Wellington to Tawa was double tracked).