A runaway trolley which crashed through a level crossing gate was not fitted with brakes, a report has revealed.
The trolley, which was carrying 1,100lbs (500kg) of ballast, hit the gate on the East Lancashire Railway (ELR) in Ramsbottom, Bury, on 15 March.
The Rail Accident Investigation Board (RAIB) report also found the volunteers using the trolley were not being supervised, but nobody was injured.
The ELR said the crash led to a "top to bottom review" of work activities.
Investigators found the trolley's make-shift brakes had been removed to allow volunteers to move it, but it had "got away" from them due to the line's gradient.
The trolley hit the gate on Bridge Street at about 11:15 GMT and spilt the ballast across the road, which was open to traffic.
The report said a supervisor was further down the line and not with the four volunteers using the trolley at the time of the crash.
Issuing an number of recommendations, the RAIB called for "guidance" from the Heritage Railway Association (HRA) on the deployment of trolleys without brakes and advised the ELR to improve the auditing of donated equipment.
The ELR spokesman said safety was of "paramount importance to us and remains our top priority".
"This incident has resulted in a top to bottom review of how we plan, manage and deliver work activities, as well as the monitoring and auditing of our safety performance," he added.
The HRA's chief executive Steve Oates said his organisation "fully agree with the need for more guidance on the use of trolleys" and had added it to their "existing coverage... as a priority".