The wagons rapidly gathered speed as the gradient increased to 1 in 72 and passed three signal boxes, none of which had points under their control to deflect the runaways.
Meanwhile, a passenger train which had left Barnsley at 18:15 was standing at Stairfoot station one and a half miles away.
The runaways struck the rear of the standing train at a speed of at least 40 mph, killing 15 and injuring 59 more.
The enquiry by Lieut-Col F. H. Rich found that the goods guard was gravely at fault for not ensuring the standing wagons were better secured.
The layout of the yard was also criticized as there were no trap points to protect the running lines in the event of such a mishap.