STRUCTURAL DAMAGE to the rail overbridge just south of Potters Bar station is so severe that it must be replaced, Railtrack engineers said this week.
Railtrack London North Eastern aims to reopen the line next week by installing temporary props under the bridge. It is expected the road beneath will be reduced to a single lane. Speed and freight restrictions will also apply to trains.
The Darkes Lane bridge was built in 1954 with three parallel spans of welded steel plate girders with a composite steel/concrete deck. The middle span carries two tracks and the outer spans one each. The most seriously damaged is the west span, which carries the line from London King's Cross towards Kings Lynn and on which the train was travelling as it crashed.
Baldwins Industrial Services is lifting the carriage trapped under the station platform roof. It is using its giant Gottwald AK912 strut jib crane, which at 1,200t capacity is the UK's largest truck mounted crane.