Rio Tinto has reopened a key Pilbara rail line linking its iron ore mines to port less than a week after a dual-incident crash that the Mining and Energy Union has seized on as evidence of safety issues around the use of driverless trains.

The West Australian rail line reopened on Saturday as Rio continues a major investigation that has already led it to suspending a procedure known as “on-site override” when it comes to the operation of its fleet of giant robot trains.