In 1955, with the opening of the Rimutaka Tunnel and deviation, a Centralised Traffic Control system was installed at Upper Hutt station to control main line points and signals between Trentham and Featherston inclusive. However, only one crossover (18) and four signals (8, 23, 23A and 29) at Trentham could be controlled from Upper Hutt; the remainder, which were typically only used on race days at the adjacent Trentham Racecourse, were controlled by a panel at Trentham itself. The semaphore signals were replaced with three-colour searchlight signals. On 6 February 2007, the Upper Hutt signal box was decommissioned and control of the line from Trentham to Featherston was moved to Train Control in central Wellington.