Accident, Walton-on-the-Naze

HC Deb 21 October 1991 vol 196 cc465-6W

Mr. Spearing

To ask the Secretary of State for Transport when he expects the publication of the report of the inspector of railways consequent to his inquiry into the accident at Walton-on-the-Naze in August 1987; on what date the inspector concerned concluded his inquiry; and if he will make a statement explaining the factors governing the timing of its publication.

Mr. Freeman

[pursuant to his reply, 14 October 1991, Official Report, column 112]: On 12 August 1987, the 13.05 train from Thorpe-le-Soken to Walton-on-the-Naze formed by a single class 313 electric multiple-unit failed to stop at the terminal station and collided violently with the buffer stop. The leading vehicle overrrode the buffers and became embedded in the station buildings. There was one major injury to a passenger who suffered a broken leg, but only minor injuries were suffered by the train crew and other passengers. Subsequent examination of the train revealed that the code conversion unit (CCU) which transfers signals from the driver's brake lever into instructions for the electrical and disc brakes of the train had a welded contact. The disc brakes are air-activated, the actual brake force being controlled by combinations of two diaphrams. One diaphragm is twice the size of the other and it is therefore possible to provide three equal increases in brake force. Hence the use of the term three-step brake. The effect of the welded contact was that step I was ineffective, step 2 was fully effective, but step 3 gave no further increase in braking effort over step 2. There is, however, an emergency position on the brake lever. In this position the signals to the CCU are, in effect, bypassed and although no extra braking effort is produced it does ensure that the maximum possible effort is available. Hence in this case selection of the emergency brake position would have ensured the full application. that is step 3, of the brakes would have occurred.

It was not possible during the inquiry to obtain a story from the driver as to how he handled the braking of his train on the approach to Walton which could be matched to the technical evidence of what braking effects were available to him. Suffice it to say that he was unaware of the difference between the step 3 and emergency positions of the brake handle and the full application of the brakes was made only when he left his driving position and released the driver's safety device shortly before impact occurred. Subsequent experiments at British Railways research centre enabled a reasonably accurate picture of the actual running of the train to be determined and hence it was possible to conclude that, despite the brake fault, the driver mishandled the braking of his train and then failed to make use of the emergency position of the brake level which would certainly have lessened the impact, if not avoided it altogether.

Immediately after the accident, a campaign check of all classes of vehicle fitted with the particular type of CCU was made. It should be noted that this type is no longer being fitted to new vehicles and later classes of vehicles have a different type. The result of the check showed that only one other CCU had a welded contact. The likely cause of this welding is external to the CCU and BR has taken measures to reduce the current rating of the controlling miniature circuit breaker and hence reduce the possibility of achieving a welding current.

The type of three-step brake fitted to class 313 units (and others) gives a maximum retardation in step 3 of 9 per cent g with, as explained earlier, no increase in brake force in the emergency position. British Railways has reviewed this and, in future, use of the emergency position will give an increased braking effort resulting in a retardation of 12 per cent. g. This new three-step-plus emergency brake will be fitted to all new builds of multiple unit rolling stock and retrospectively to all existing builds of electric multiple units.

The inspecting officer of railways who held the inquiry is satisfied that immediate action was taken to determine whether similar faults of the trains' brakes were present elsewhere and to limit still further the likelihood of their occurring in future. He is also satisfied that the newer CCU is an improvement on the old and he welcomes the decision to provide increased braking effect when the emergency position of the brake lever is used.