While the official inquiry found the primary cause of the crash to be poor fastening of the track, there were a number of factors that were identified as contributing to the accident.

[2] The train involved in the disaster consisted of eight wooden bodied Supplementary Interurban Passenger Carriages, which had been converted from country passenger stock by the PTC, which were hauled by 46 class electric locomotive 4620, which had commenced its journey towards Sydney from Mount Victoria in the Blue Mountains at 6:09 a.m.[3] At approximately 8:10 a.m. it was approaching Granville railway station when the locomotive derailed and struck one of the steel-and-concrete pillars supporting the bridge carrying Bold Street over the railway cutting.

[5] Of the total number of passengers travelling in the third and fourth carriages, half were killed instantly when the bridge fell on them, crushing them in their seats, some to the point where their head and shoulders were below the level of their knees.

Some of these injured had been conscious and lucid, talking to rescuers and explaining their experiences of the event, however, most died of crush syndrome soon after the weight was removed from their bodies.

Rescuers also faced the greater difficulty of the weight of the bridge, which was still crushing the affected carriages and reducing the available space in which they could work in to rescue survivors.

[7] Several of the deceased were overcome by the gas leaking from ruptured cylinders, reducing the amount of available breathable air in the area underneath the bridge.

Locomotive 4620 had been involved in a similar accident twelve years earlier, when it had derailed at Wentworth Falls in the Blue Mountains when operating a freight service.

The disaster prompted substantial increases in rail-maintenance expenditure, something that had been experiencing a deficiency decline since the Second World War due to the reduction available of materials, finances, and labour forces.

The Public Transport Commission of NSW soon after the accident immediately began a systematic process of track maintenance in order to prevent another incident like this from occurring.

It was found that some infrastructure, including track and overhead bridges, had been seriously under financed over a number of years, reducing the network to the point where another accident similar to Granville would occur.