"Lessons have been learnt" over an IT failure which allowed a train to approach a level crossing at nearly three times the speed limit.
A problem sending data to the train on the Cambrian Coast line meant it was travelling at 80km/h (50mph) rather than 30km/h (19mph) on 20 October 2017.
The report into the incident in Gwynedd made five recommendations, including improving computer safety measures.
Network Rail said it was reviewing the introduction of safety software.
It told BBC Wales it took "the findings of this investigation report very seriously" and it was "reviewing current processes for the introduction of complex safety critical software in light of them".
The Rail Accident Investigation Branch (RAIB) report found temporary speed limit data was not uploaded to trains during a computer restart the previous evening on the Cambrian line.
The 08:52 Machynlleth to Pwllheli service then travelled between Barmouth and Llanaber at about 80km/h, in a section limited to 30km/h.
The driver of the train reported a fault with the information on his computer screen and technicians in the control room found the speed limit information had not been sent to any trains on the line.
They restarted the system while signallers and drivers reverted to verbal and written instructions to allow trains to continue running.
The speed limit had been in place since 2014 to give level crossing users plenty of warning of approaching trains.
Network Rail said: "The lessons learnt from this incident have been considered very carefully in terms of their applicability on our network.
"Processes have been and continue to be reviewed and updated as required to mitigate against such scenarios."