The NSW opposition claims photographs taken by the driver show a CityRail train travelling at speeds of up to 60kmh with no driver at the controls.

Under the "deadman's" braking system, the train should stop the moment the driver steps off a defined spot at the controls.

An inquiry into the 2003 Waterfall train disaster blamed the tragedy on a faulty deadman's brake which failed to activate when driver Herman Zeides suffered a heart attack, causing the train to derail.

The rail union today urged the NSW government to implement a new computerised emergency braking system to improve commuter safety.

RailCorp, however, said trains were "substantially safer" than before the Waterfall crash, in which seven people died, thanks to a second backup braking system.

RailCorp chief executive Vince Graham said the Waterfall inquiry found the deadman's brake was not 100 per cent effective, so millions had been spent on installing a second "vigilance" braking system in all CityRail trains.

The vigilance system locks the brakes automatically within 60 seconds if the driver does not respond to the train's controls or becomes incapacitated.

Mr Graham said there was nothing in the photographs to suggest the vigilance system was not working.

"There is no 100 per cent effective deadman's system anywhere in the world, so while we check the deadman's braking system prior to trains entering service every day, you can have defects," Mr Graham said.

"Those vigilance braking systems have been fully commissioned on all of our fleet for more than 12 months ... and they have made our trains substantially safer than they were at the time of the Waterfall disaster."

Rail, Tram and Bus Union state secretary Nick Lewocki said drivers were required to ensure the deadman's brake was working before setting out on a journey.

Mr Lewocki said the government could improve emergency stopping systems in CityRail trains by installing the computerised "automatic train protection system" used on Perth's rail network.

"(That system) ensures a driver cannot exceed the posted speed limit and the train cannot pass a signalled stop," he said.

NSW opposition transport spokesman Barry O'Farrell said that regardless of the effectiveness of the new vigilance system in CityRail trains, photographs of a driverless train travelling at 60kmh were worrying.

"These photos of a train travelling at 60 kilometres per hour without a driver operating the controls raise serious concerns about the effectiveness of the new system," Mr O'Farrell said.

NSW Transport Minister John Watkins said rail safety was the Iemma government's top priority.

"Nothing is more important than the safety of our public transport services," he said.