Train crashed into 425ft rail left on track after repairs
The collision near Inverness on February 25 was the latest in a series of incidents.
An Inverness train crashed into a 425ft-long length of rail which had been left on the track after repairs.
The collision near Cradlehall on February 25 was the latest in a series of incidents where lines were left unsafe after engineering works, according to a watchdog.
The 53mph impact pushed the rail off the track, preventing the Virgin East Coast Inverness to London train from derailing.
There were three similar incidents in England between 2014 and 2017, the Rail Accident Investigation Branch said.
The organisation has issued urgent safety advice to Network Rail to prevent future incidents.
It warned: "Over the last four years there have been a number of incidents in which railway lines have been returned to service in an unsafe condition following engineering work.
"In all such cases there is a real potential for serious harm to people on subsequent train services.
"In light of these incidents -and given the serious nature of the most recent incident - the RAIB advises Network Rail to take urgent steps to review the effectiveness of the steps it has already taken to address this risk and to implement any additional measures that are required."