A worker hit by a train going around 25mph near Chalfont and Latimer station was carrying out a scheduled track investigation, investigators have said - as they try to figure out why she was hit when there was a system in place to keep staff away from moving trains. 

The woman was taken to hospital for treatment after being hit by a London Underground Metropolitan Line train that was going from Baker Street to Chesham at around 9.30am on Friday, April 15. 

The shocking incident is being investigated by the Rail Accident Investigation Branch (RAIB). 

The RAIB said the woman was part of a group of three staff members who were carrying out a scheduled track inspection on a section of the line used by trains running in both directions. 

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The maximum speed permitted in 35mph and the train that hit the woman was being driven at around 25mph. 

The work was planned to take place while the lines were open to traffic, with a system of work in place intended to keep staff away from moving trains. 

The RAIB investigation is trying to determine what led to the worker being hit and will look at the actions of the workers involved, the planned system of work, the arrangements that were in place for planning work where lines are open to traffic, the management of the competence of track workers and any other relevant underlying factors. 

Their findings will be published, which will include any recommendations to improve safety, once the investigation is complete.