Train passed red danger signal before crash

Preliminary findings of Sunday's collision

The Rail Accident Investigation Board (RAIB) has provided an update about a collision on Sunday evening involving a service heading from London to Hontion and another from Portsmouth Harbour to Bristol.

The trains hit one another in a tunnel near Salisbury around 6.45 p.m.

The impact of the collision caused the front two coaches of one train and the rear two coaches of another to derail. Both trains continued some distance into Fisherton tunnel following the collision, before they came to a stop. Thirteen passengers and one member of railway staff required treatment in hospital, and the collision caused significant damage to the trains and railway infrastructure involved.

RAIB’s preliminary examination has found that the movement of the Portsmouth train across the junction was being protected from trains approaching on the Down Main line by signal SY31, which was at danger (on red ). The Honiton-bound passed this signal, while it was at danger, by around 220 metres, immediately prior to the collision occurring.

Preliminary analysis of data from the On Train Data Recorder (OTDR) fitted to the Honiton train shows that the driver initially applied service braking to slow the train on approach to the caution signal before signal SY31. Around 12 seconds after service braking started, the driver made an emergency brake demand. As the train approached signal SY31, and with the emergency brake still being demanded by the driver, a second emergency brake demand was made by the train protection and warning system (TPWS). These emergency brake demands did not prevent the train from reaching the junction, where the collision occurred. OTDR analysis indicates that wheel slide was present both when the driver applied service braking and after emergency braking was demanded. This was almost certainly a result of low adhesion between the train’s wheels and the rails.   

The investigation will seek to identify the sequence of events which led to the accident. It will also consider:

• the level of wheel/rail adhesion present on the approach to Salisbury Tunnel junction
• the status and performance of the braking, wheel slide protection and sanding systems on train 1L53
• the behaviour of both trains during and following the collision
• South Western Railway’s policies relating to low wheel/rail adhesion
• Network Rail's policies relating to low wheel/rail adhesion and how they managed the risk of low adhesion in this area
• the processes used to assess and control the risk of overrun at signal SY31
• any relevant underlying factors, including any actions taken in response to previous safety recommendations

The investigation is independent of any investigation by the railway industry, the British Transport Police or by the industry’s regulator, the Office of Rail and Road.