Article written by Simon Cave – Sector Lead – Rail, and Senior Principal – Project Management
The Lower North Island Rail Integrated Mobility (LNIRIM) programme is a step-change for regional rail. At its heart is Tūhono, a fleet of 18 five-car battery-electric multiple unit (BEMU) trains, the first of their kind in the Southern Hemisphere. These trains will replace ageing diesel-hauled services on the Wairarapa and Manawatū lines, with the first units expected from 2028 and expanded services rolling out from 2030. Alstom has been selected to build and maintain the fleet.
Beyond the trains themselves, LNIRIM funds the infrastructure that makes a frequent timetable possible. This includes new and extended passing loops, additional stabling in Wellington and Palmerston North, a new depot and stabling facility in Masterton, and selected station and track upgrades. Together, these works create operational flexibility to add services, recover from delays, and reliably meet peak demand. Ministry for the Environment.
In parallel, the Wellington Metro Substations Programme delivers the power capacity and resilience the network requires. The Government has committed $137.2 million to renew and upgrade substations across the metro network, many of which are 60–90 years old, specifically to improve reliability and enable future growth in services. This is the quiet, critical backbone for performance, stronger substations will reduce voltage sag, protect assets, and provide headroom for more trains.
The relationship is straightforward. LNIRIM adds new trains and timetable ambition, while the substations provide the electrical capacity and reliability to sustain the enhanced regional rail timetable, as well as timetable enhancements within the Wellington Metro Area for existing metro services.
Vitruvius is contributing on both sides of this “capacity and service” equation. For the Metro Substations Programme, we are providing civil design services including site access upgrades, building formation and retaining wall design, site security fencing, drainage and flood protection improvements, and new ducting to enable incoming and outgoing power and fibre connections. On the LNIRIM yard upgrades, we have recently been appointed Lead Consultant for the Masterton and Palmerston North facilities. Here, we are coordinating the multi-disciplinary design of stabling, servicing, and operational layouts that will accommodate the Tūhono fleet and support the uplifted timetable. These facilities are pivotal to reliable day-to-day operations and rapid turnarounds between peaks.
Together, these programmes will deliver cleaner trains, more dependable power, and the infrastructure to run more services more often on the NIMT and Wairarapa lines. The result is better access to jobs and education, stronger inter-regional links, and a network that can grow with demand rather than be constrained by it. That is the promise of Tūhono — to connect and unite communities — and it is a promise Vitruvius is proud to help make real.