Design of points under scrutiny

Investigations into the Potters Bar train disaster took another twist today as Railtrack raised speculation that the design of track points may have contributed to the tragedy.

In effect, it says that the threaded "stretcher" bars which hold the points together may have been too short with not enough left poking through after locking nuts were tightened. This increased the risk that the nuts, having worked loose, could have more easily dropped off.

With two stretcher bars loose at Potters Bar, this put added pressure on a third which broke as the four-carriage King's Cross to King's Lynn train was passing over the points at 100mph last Friday.

The points changed direction, derailing the last carriage which then smashed into the station, killing seven people and injuring 76, 10 of them seriously..

Railtrack has now issued a nationwide "special investigation notice" (SIN) which instructs track staff to carry out an extra inspection on 867 sets of points similar to those at Potters Bar to ensure there is enough of the threaded stretcher bar visible after the nuts have been tightened.

Mick Cash, deputy general secretary of the RMT, largest of the rail unions, said: "The SIN is an admission by Railtrack-that there could be something wrong with the equipment.

"It calls into question the use of adjustable stretcher bars, the design of which has been imported from the Continent, and whether they should be replaced with an alternative locking method."

Mr Cash, a mainline signal technician with specialist knowledge of the track and points system, added: "The fact that this notice has been issued indicates that something is wrong.

"This is not a reflection on the track employees who have to work to the standards laid down by Railtrack but about the equipment."

A spokesman for Railtrack confirmed the notice, SIN 80, had been sent nationwide and covered all sets of points that are of similar design to those which caused the Potters Bar derailment.

He said: "It is basically a precautionary-measure to check that nuts are secure on stretcher bars." The inspection, he added, is in addition to other checks which have already been carried out. "We have not found anything that shows there is an endemic problem."

The notice, however, will cause increased concern over the design of stretcher bar and whether a different and "failsafe" locking mechanism of the adjustable bars should be used.

Earlier this week, crash investigators revealed that in the wake of the derailment, all 867 sets of similar points were checked and that some nuts had been found loose and needed tightening.

The Health and Safety Executive, in a preliminary report, revealed that one pair of the 2in-wide nuts had been found missing from the set of points 2182a south of Potters Bar station. They were found lying beside the track during an inspection carried out by three employees of contractor Jarvis Rail on 1 May, 10 days before the crash.

They were replaced by the maintenance workers and tightened up again. After the derailment, it was found that a total of four nuts were found to have come off two of the three "stretcher" bars that are vital for the safe working of the points.

Work continued at Potters Bar today to install new points and repair the track and station. It is hoped to have a limited number of trains running again from Monday.