CONFUSED Marsden residents were left wondering if there had been a major accident as emergency services descended on the village yesterday.
But the incident was a training exercise involving a fictitious Standedge Tunnel train accident.
From 9.30am, fire engines and ambulances congregated at the Standedge Visitor Centre car park.
Ambulances also waited on call in nearby Slaithwaite.
A control centre for the operation was set up at Marsden railway station.
Representatives of British Transport Police, Network Rail, British Waterways, the National Trust and Raynet - the Radio Amateurs Emergency Network - were based there.
Oldham Mountain Rescue Team was also there, developing a search plan for the tunnel to ensure that in a real emergency no casualties would be missed.
The exercise was co-ordinated by Network Rail and British Waterways.
Each agency had a specific plan for such an incident, including site management, vehicle management, communications and search and rescue procedures.
Richard Davies, Network Rail exercise director, said the idea of the event was to ensure all the plans linked together properly.
He said: "This exercise was about logistics - making sure we get the right people to the right places."
The plans for each agency were drawn up at a training day in Oldham in October 2002.
They are specific to the Standedge Tunnels, because of their unique structure.
It has working and disused rail tunnels and a linked canal tunnel.
The simulated emergency took place on one of the disused lines and the canal was closed to boat trips during the event.
Alex Pilling, Network Rail spokeswoman, said: "We hope we can transfer lessons we learn to work on other long tunnels in the UK."