Robin Grigsby of Network Rail (Letters, June 16) appears to be trying to play down the statement in Network Rail's own plans for Southern routes, as quoted in the latest edition of Modern Railways in an article by the reputable railway journalist Ken Cordner.

The article reports that "rolling contact fatigue (RCF) has affected the Brighton main line extensively and further rerailing and switch and crossing replacement is planned, along with extensive rail grinding.

"Network Rail's plan says: 'The impact of the introduction of Class 377 rolling stock on track renewal and maintenance requirements is still being assessed, taking into account the higher tonnages of the new trains.

"'It is anticipated the suspension characteristics of new trains will lead to a significant growth in RCF propagation with consequent impact on track maintenance activity'."

So this is not scaremongering - we are talking about Network Rail's own assessment of the situation.

Clearly there is something peculiar about the suspension of the new trains - the slightest irregularity in the track sets the carriages wobbling and this may be related to the effect they have on the track.

Rolling contact fatigue is the type of track damage that led to the Hatfield derailment four years ago and, following that incident, attention was focussed on the interaction between wheel and rail; the train wheel makes contact with the top of the rail over an area about the size of a small coin.

This interaction is complex and not fully understood, which is why it was a mistake to change the entire fleet of rolling stock over such a short period - it should have been phased in over at least a decade, so that design faults could be identified and rectified.

Part of the blame lies with John Prescott for rushing through, at a cost of about £3 billion, the elimination of the slam door stock on "safety" grounds, even though there are more accidents in the bus lanes of Brighton than the entire slam door territory.

-Henry Law, Brighton