NIMT electrification – a project with a history

Electrification of the North Island Main Trunk line between Auckland and Wellington can be viewed as both an engineering triumph and a philosophical conundrum.

The 411 kilometre section between Palmerston North and Hamilton was electrified at 25 kV 50 Hz AC and opened in June 1988. It ranks as one of the most significant engineering projects in the history of New Zealand Railways.

The project was one of the so-called “Think Big” projects of the Muldoon era and a response to the oil price shocks of the 1970s and early 1980s.

An overall cost in excess of $100 million had been projected but the final cost was about $250 million. Defenders point out that a significant proportion of this sum went on realignment of the rail corridor and improved signaling, projects that would have provided a benefit regardless of electrification.

The economic benefits of the project were reduced by the fall of the price of oil in the later 1980s and the deregulation of land transport, which removed the long distance monopoly NZR held when the cost benefit report was written.

Electrification of the North Island Main Trunk almost happened 30 years earlier – and it generated the same passions and arguments as its eventual successor.

In 1949, the General Manager of the Railways Department, Frederick Aickin advocated electrification of the entire line, in spite of protests from some of his engineering staff.

Following the Second World War, railway services suffered from skill, locomotive and coal shortages. Aicken believed electrification could relieve the coal situation and prevent heavy spending on imported fuels.

Aickin sent a technical mission of four senior officers overseas in March 1949, and travelled overseas himself to negotiate a tentative contract with a British construction company. The Chief Mechanical Engineer and Chief Accountant specified and costed the system and Aickin submitted a substantial report justifying the NIMT electrification.

Staff from New Zealand Treasury, the Public Works Department and two experts from Sweden commented on the proposal and in December 1950 the Government granted approval in principle. However, Aickin’s retirement as General Manager in July 1951and a change in thinking from his successor resulted in the plan being shelved.

A Royal Commission on Railways established following Aicken's tenure, side-stepped the proposal, leaving it to Aicken's successor, Horace Lusty, to terminate the tentative consultancy contract.

He was sceptical of Aickin’s projections for traffic growth on the Trunk. He initially considered existing steam locomotives could cope with demand and then subsequently ordered DA class diesel electric locomotives.

A key assumption of Aicken's report was that traffic on the NIMT would grow by 50 percent from 1948 to 1961.

Since a diesel-electric locomotive was in fact a travelling power station, the savings through electrification compared to diesel could be regarded as the difference between the cost of buying bulk electrical energy generated substantially from New Zealand resources and the cost of generating electricity in small plant using imported diesel fuel - although there was also significant expenditure on traction overhead and other new capital works to take into account.

The section of railway line between Te Rapa near Hamilton and Palmerston North remains the only significant section of electrified railway outside the Wellington metropolitan network and the Auckland metropolitan network.