Driver error contributed to a train accident outside Johannesburg last year that left 857 passengers injured, a board of inquiry said on Friday.

"It was very clear to the board of inquiry that the driver was a high-risk individual," board investigator Chris Dutton told reporters in Johannesburg.

He was releasing an official report by the Rail Safety Regulator (RSR) on the accident in May last year.

It happened when a train from Johannesburg to Naledi crashed into the rear of a stationary train on the same track, between Mzimhlophe and Phomoleng stations.

The report said the driver had ignored two warning signals and was speeding.

Dutton criticised disciplinary procedures at Metrorail, operated by the Passenger Rail Agency of SA (Prasa), that allowed the train driver to continue his conduct.

"Did section managers not pick up on the risk?" asked Dutton.

The report said the driver had previously been cited for speeding - three times in two years.

He had not signed off properly at another time and had ignored a lawful instruction from supervisors in August 2010.

He had also been responsible for a train delay and had once been late for duty.

The report said the driver could have been given warnings based on each infraction, and suspended from driving, following the third incident of speeding.

"Because the procedures were not followed, the driver was still on the footplate," Dutton said.

The driver has since been dismissed from Metrorail.

The board said the driver could have also gone to refresher courses and been put under observation. However, observation was not possible due to a high number of vacancies of section managers at Metrorail.

The report slated Metrorail for its communication system and track maintenance as underlying causes of the accident.

Train operators did not have working radios and had to rely on cellphones to communicate with stations.

Train drivers were given R200 of airtime a month, but this was not enough -- so text messages instead of voice calls were used.

The inquiry found the two trains were on the same track because another track was not repaired after it had been washed away in a storm months before the accident.

The trains involved were also overloaded with passengers, worsening the accident.

"In a railway accident, it is not the result of a single incident," said Dutton. "It is the culmination of a series of parallel events."

RSR CEO Nkululeko Poya said Prasa had promised to consider the report's recommendations.

"Every time we issue a report, we expect a response... and that response must address how they will deal with those issues," Poya said.

He said Prasa would have to look at several issues, including the scheduling of trains and access to platforms, both of which contribute to how overloaded a train might be.

RSR chairperson Brenda Madumise said that management at rail services had to be able to hold the management of operators to account when accidents occur.

"It has to stop at some point, where management has to take responsibility. It cannot be lower-level employees all the time," Madumise said.