Hutt from 2021 to 2024 include track renewals with full renewal in the Remutaka and Maoribank tunnels, renewals of timber elements in three bridges, refurbishments of some level crossings and drainage and vegetation clearing. In November 2021, Greater Wellington Regional Council proposed the purchase of tri-mode multiple units for the line, similar to bi-mode multiple units used overseas. Electrification Proposals have been made to extend the electrification into the Wairarapa and the Rimutaka Tunnel was constructed to allow overhead lines to be installed, although before opening diesel operation was adopted. In 2007, the Greater Wellington Regional Council rejected a call for the line to be electrified to Masterton, stating that patronage was too low to justify the capital expenditure. In May 2021, KiwiRail, Beca and Systra published the North Island Electrification Study, which put forward two options for electrification expansion for the Wairarapa Line from Upper Hutt to Masterton: Option 1: electrify the entire section at 25kV AC (same system as Auckland and central NIMT), with a voltage changeover at Upper Hutt; Option 2: use battery-electric EMUs with two 7km long overhead segments around Featherston and Masterton at 1600V DC. The estimated costs of option 1 was $226m, with option 2 being $82m. Signalling The Wairarapa line used four of the six New Zealand railway signalling systems: Double Line Automatic (DLA), Centralised Traffic Control (CTC), Track Warrant Control (TWC) and Station Limits. Signalling at Petone is future-proofed for conversion to a fifth system, Automatic Signalling Rules (ASR). The Wairarapa Line had a number of lasts for railway signalling in New Zealand Semaphore Signal on an operational line, these were decommissioned in 1996 however the masts (poles) remained in place until July 2014. Line controlled by Tyers Electric Train Tablet Manned signal box outside of a major station Prior to the Trentham–Upper Hutt–Featherston section being transferred to Train Control in February 2007, this was the last section with CTC controlled by a signalman. Part-time signal boxes remained at Petone (weekday peak and inter-peak) and at Taitā (weekday peak) until December 2013 and July 2014 respectively, when signalling was switched to Train Control in central Wellington. Masterton is a unique signalling arrangement with Track Warrant Control ending at 'TWC Ends' boards north of the two-position home signal, which allows shunting movements to be carried out without the need for a Track Warrant. Along with Horotiu (on the NIMT between Te Rapa and