The milestone trip, spanning nearly 100 km (60 miles) with trains operated by individuals in an air-conditioned control room hundreds of kilometres away, puts Rio Tinto on track for commissioning the so-called AutoHaul project in late-2018, the miner said.

The company, one of the first to ever embrace driverless mining vehicles, already runs about 200 locomotives on more than 1,700 km of track, hauling ore from 16 mines to four port terminals.

Rio’s trains began running in autonomous mode in the first quarter of this year and about 50% of its pooled fleet rail kilometres are being completed in autonomous mode, but with drivers on-board.

The company said that 90% of its pooled fleet production tonnes are AutoHaul enhanced, which means they are able to operate continuously without shift changes and improved safety, with trains responding automatically to speed limits and alarms.

Rio Tinto said it has already seen the benefits from AutoHaul in increased train speeds and fewer stops that have cut more than an hour from average journey times.

Getting to this point was not easy. The actual commissioning of the autonomous trains project has been put off a few times, partly due to software problems.

Delays with the implementation of autonomous iron ore trains hurt Rio Tinto’s output in 2016. The miner ended up producing 330 million tonnes, down from the original target of 350 million tonnes.

The so-called Autohaul plan is part of the “Mine of the Future” project the company launched in 2008 and which also included the introduction of autonomous haulage trucks, automated drilling and the roll out of an operations centre near Perth airport.