On Monday, February 7 last year the grain transporter, en route from West Wyalong to Port Kembla, lost control over a 3km section of track south of Unanderra station, just after 6.30am.

No-one was hurt in the incident, which was the subject of a scathing safety report that has been tabled in NSW Parliament.

One of the state’s chief safety watchdogs, The Office of Transport Safety Investigations (OTSI), has raised questions about the drivers’ actions, including their ability to use the braking systems, their knowledge of the instruction manuals and their use of mobile phones to raise the alarm.

The train was carrying 40 wagons at the time, 39 of which were loaded with grain. The train broke speed limits on multiple occasions during its descent, at one point travelling at 68km/h, before slowing to a stop on a gentle gradient north of Unanderra station.

Train operator El Zorro has defended its drivers, who it said were well trained and knew how to operate the train on that slope.

The OTSI found that the chief cause of the incident was the drivers’ failure to properly use the braking systems.

During the descent the driver briefly switched off the train’s electrical braking system, which subsequently lost power. The air brakes also became depleted after at first being pressed too lightly and then too heavily.

‘‘The train became uncontrolled during its descent because the manner in which it was driven did not provide for effective braking.

‘‘Initial braking effort was too ‘light’, but then was progressively increased until a full brake application was achieved ... at a critical point in the sequence of events, braking became unbalanced when the dynamic brake was disengaged and then re-engaged,’’ the report stated.

OTSI investigators later interviewed the drivers, who the report claims did not appear to know the difference between different braking methods.

‘‘It was evident that the driver did not understand the difference between serial and balanced braking techniques which are used for descents like the Illawarra Mountain,’’ the report said.

El Zorro transport general manager Nick Papadopoulos said drivers were aware of the different braking techniques, ‘‘but did not understand the term’’.

The report states that at the time of the incident El Zorro had no policies or procedures for the control of trains descending the section of track. Manuals had not been updated since 2004, with 592 amendments not inserted.

Mr Papadopoulos said it was the responsibility of the railway track manager, the Australian Rail Track Corporation (ARTC), to keep its manuals updated.

An ARTC spokeswoman said the corporation was ‘‘considering the OTSI’s recommendations’’.

But she said the incident occurred in RailCorp-controlled territory and that ‘‘the cause of this incident appears to be the use of the braking system on the train’’.

OTSI Investigators also questioned the drivers’ knowledge of instruction manuals.

During interviews the drivers ‘‘gave the impression of not having a full understanding of these train operating conditions manual requirements, although the co-driver’s understanding appeared to be better than the driver’s’’, the report stated.

Drivers also failed to use the train’s internal radio to raise the alarm, relying instead on mobile phones, according to the report.

The driver at the centre of the affair was immediately restricted to co-driver duties after the incident, according to the report.

He was also eventually returned to northern NSW to operate trains ‘‘where gradients are less severe and the driving demands are not as stringent’’.

Mr Papadopoulos said El Zorro ensures its ‘‘drivers are fully competent and accredited in all rail corridors and have a full understanding of all rolling stock on the train.’’

He said the drivers were well trained and signed off as competent by instructors with 20 years of experience driving trains on the steep corridor.