Catenary power – the overhead wires that supply energy to countless trains and trams – is fundamental to transport, and now there are some big visions to take it off the rails.
While electric cars, buses and trucks have recently become a common sight on Australian streets, it is far from the first time.
In fact, 80 years ago, a visitor to almost any major city would have encountered frequent trolleybuses, their tyre-clad wheels powered by overhead electric wires. Clean, quiet and efficient, trolleybuses were killed off by their inflexibility – tethered to the grid, they couldn’t navigate around a simple traffic snarl – and faltering economics.
By the 1960s, diesel engines and fuel were cheap enough for transport authorities to accept the noise and fumes, wiping out the trolleybus networks.
Today, however, the principle behind the trolleybus is making an engineered comeback. Faced with the immense challenge of decarbonising heavy transport, engineers are looking back to direct electrification to power some of our heaviest vehicles.
High-wire act
Nowhere is the challenge greater than in open-pit mining, where haul trucks burn vast quantities of diesel pulling loads up long ramps. These sites, with their fixed, high-energy routes, have become the perfect incubator for reinventing catenary technology.
The first step was the diesel-trolley hybrid. Trucks connect to overhead lines on the most demanding, energy-intensive uphill segments, dramatically cutting fuel use.
Collahuasi copper mine in Chile, for example, installed catenary power on a 1 km section of ramp. The four 365 t Liebherr trucks have more than doubled their uphill speed – from 11 to 25 km/h – while diesel consumption and carbon dioxide emissions on that segment have fallen 98 per cent.
This “bridge” technology is being advanced by manufacturers such as Komatsu, whose Power Agnostic haul truck platform was first deployed at Sweden’s Aitik mine in July this year. Its modular architecture allows a mine to start with a diesel-trolley system and later transition to battery-electric or hydrogen power without replacing the entire vehicle.
The next evolution is the battery-electric trolley, which uses the catenary not just for propulsion, but for dynamic charging. The truck is fully electric, and the overhead line recharges its batteries while in motion, cutting downtime. Hitachi Construction Machinery and ABB are trialling this approach.
Innovative engineering is also tackling the primary drawback of traditional catenaries: the fixed, costly infrastructure.
Instead of a 15 m-tall overhead mast system, Liebherr’s Power Rail concept uses a side-mounted conducting rail just a third the height, making it faster and easier to install and relocate.
Hitting the highway
Worldwide, road freight is a major emissions source. In Australia, heavy trucks are responsible for more than two-fifths of all transport emissions. The fact that heavy road freight is normally concentrated on major arterial routes has made it an attractive target for catenary power.
Germany has been leading the direct electrification of trucking, building multiple short stretches of “eHighways” since 2017.
There, Professor Alan McKinnon of Hamburg’s Kühne Logistics University, estimates 60 per cent of heavy truck carbon dioxide emissions occur on just 2 per cent of the road network, while almost 90 per cent of freight trucks cover fewer than 50 km or less after leaving the highway. In German and Swedish trials by Siemens and Scania, trucks use a small on-board battery for the first and last miles.
While eHighway trucks require significantly more infrastructure than traditional trucks or even battery-electric trucks, they bring other advantages.
One is their efficiency, thanks to minimising conversion losses. The German government estimates eHighway trucks have a well-to-wheel efficiency of 77 per cent, compared to 62 per cent for battery-electric trucks and 29 per cent for hydrogen fuel-cell trucks. Traditional diesel trucks average 20-25 per cent.
With no need for heavy, long-range batteries, eHighway trucks are also lighter. This means they can carry more goods – making their efficiency even higher. By lessening dependence on batteries, they also reduce the high energy and resource costs of manufacturing batteries. Lastly, the continuous power also eliminates refuelling or recharging stops.
Despite the high upfront costs of investing in catenary infrastructure, one major German study estimated that electrifying between one-third to half of Germany’s autobahn network would be the cheapest way to decarbonise road freight.
Other studies have arrived at similar conclusions. For example, Cambridge University’s Centre for Sustainable Road Freight concluded that “overhead catenaries and compatible [heavy goods vehicles] are the most energy-efficient and cost-effective solution to fully decarbonise the UK’s road freight network”.
“The investments in pantograph electric vehicles would pay back the vehicle operators in 18 months (through lower energy costs) and the electrification infrastructure could pay back its investors in 15 years (through electricity sales),” the authors argued in the 2020 paper.
Different approaches
Overhead wires and pantographs aren’t the only way of directly electrifying road transport.
- Catenary systems using overhead power lines, and trucks equipped with pantographs. This approach is familiar from trams and trains, and is by far the most widespread and advanced.
- Wireless induction systems use coils installed under the asphalt, which transmit power into the vehicle without direct contact. The same technology is used for charging electric toothbrushes, and increasingly for mobile phones and other devices.
- Electric rails in the road, where a movable arm extends from the truck to the rail. This system operates like a slot car track.
Shifting roadblocks
Despite the clear technical advantages, the path to adoption is fraught with challenges.
The most significant is the classic chicken-and-egg problem: haulage companies won’t invest in catenary-capable trucks without the infrastructure, and governments or private entities won’t fund expensive infrastructure without a fleet of vehicles ready to use it.
Further, social and political acceptance remains low. Research in Germany reveals that while industry actors are open to the technology, the public has a poor understanding of it, and local residents are concerned about visual impact and safety.
For Australia, these developments are profoundly relevant. Our economy relies on road freight and resources – two areas where this technology shows promise. Australian mines are trialling trolley-assist haul trucks and loaders as part of their electrification. But eHighways look like being a longer haul. They could potentially help decarbonise vital freight arteries such as the Hume, Pacific, and Bruce highways, but the tyranny of our distances make it challenging.
EA OnDemand: Join Emeritus Professor Graham Town of Macquarie University to learn more about transport electrification and the grid.
This story was originally published in the November 2025 edition of create with the headline “Caternary power”.
