Rio Tinto has grown its driverless truck fleet to 53 vehicles across four mine sites, setting a new milestone in its autonomous haulage capacity.

The miner's CEO Sam Walsh told its annual general meeting in London last night the fleet had "moved more than 150 million tonnes of material" — up from 100 million tonnes a year ago.

"To put this in perspective, this would amount to filling Wembley Stadium approximately 80 times," Walsh said.

The rapid shift in tonnes moved is yet another indicator of the level of Rio Tinto's investment in autonomous technology. It took over four years to achieve the first 100 million tonnes of material moved.

Rio Tinto eventually expects to run a fleet of 150 Komatsu driverless trucks.

Vehicles are so far operational at its West Angelas, Yandicoogina, Nammuldi and Hope Downs 4 iron ore sites. Each truck is capable of shifting around 290 tonnes per load.

Walsh said the trucks had "significantly enhanced" haul cycle times, extended tyre life, reduced fuel usage and lowered maintenance costs.

More broadly, he said Rio Tinto had run some "1500 individual initiatives that focused on driving productivity gains and reducing cost" over the past financial year.

"These types of incremental improvements have a direct impact on the bottom line, and help us power our operational performance," Walsh said. "While … initiatives may not sound considerable in isolation, together they all make a substantial difference."

Rio Tinto delivered its first quarter production update prior to the London meeting, reporting "record" iron ore production, shipments and rail volumes, despite site closures for a tropical cyclone.

However, the result fell short of analyst expectations.