A train driver was hit in the face by shards of glass after a brick was thrown at the windscreen of the cab he was driving.
The brick smashed into the train as it travelled towards Clifton in Greater Manchester at around 10pm on Friday, 4 February.
The driver – who has not been named – was taken to hospital for treatment and is now recovering at home.
Northern is offering a £1,000 reward to anyone who provides information that leads to a conviction after the British Transport Police launched an investigation into the incident.
The operator’s regional director, Chris Jackson, said: “It’s hard to believe that anyone would put the safety of others at risk by such reckless behaviour.
“The consequences of a brick hitting a fast-moving train are potentially devastating.
“This was a shocking incident that could have had fatal consequences.
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“Officers are investigating, and I am appealing to anyone with information about the incident to come forward.
“Someone will know who did this and we need to find them before they do something similar which may have far worse consequences.”
Anyone with information is asked to contact the British Transport Police by texting 61016 or calling 0800 405040 or call Crimestoppers, anonymously, on 0800 555 111