A man died when he was struck by a train as he crossed a footpath in foggy conditions.
The Rail Accident Investigation Branch (RAIB) is looking into the death on 6 February at the Tibberton No. 8 footpath crossing near Worcester.
It said the 72-year-old was hit by a train travelling from Nottingham to Cardiff at 99 mph (158 km/h).
It will be looking at the measures in place to deal with the risks of using the crossing in fog, it added.
British Transport Police said the victim, from Birmingham, died at the scene just after 10:00 GMT.
It added the incident was not being treated as suspicious and a file was to be prepared for the coroner.
The RAIB said evidence shows another train, travelling in the opposite direction, had passed the crossing shortly before.
It added: "The member of the public had been waiting at the crossing for the passage of that train.
"He then started to cross seemingly unaware that another train was approaching.
"The weather at the time of the accident was foggy."
The RAIB said it will also consider the relevance of the passing of the two trains in the region of the crossing in its investigation.
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