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Investigation into the partial failure of 'bridge 94', Bromsgrove Stream, Worcestershire, on 6 April 2011

The RAIB is carrying out an investigation into the partial failure of a brick arch culvert carrying a stream under a four track railway and three adjacent sidings, south of Bromsgrove station, on 6 April 2011.

During the evening of 6 April an inspection of the line revealed an unusual dip in the track and a speed restriction of 20 mph (32 km/h) was imposed on three of the four lines at this location.

Just before 06:00 hrs on the following morning (7 April) all lines were blocked to permit divers to inspect the culvert that passes under the line.  The divers discovered that the central (oldest) section of the culvert was in a poor condition.  At this location the culvert is about 1.8 metres wide, 1 metre high and comprised a 3-ring brick arch supported on brick abutments.  The profile of crown of the brick arch had become flattened and a 600 mm x 600 mm section of the arch had partially failed, allowing ballast to drop from the track bed above into the watercourse.

Following a review of the damage, one of the four running lines was reopened to traffic at 08:28 hrs, and another at 17:00 hrs.

Traffic was not restored on all four running lines until 8 April (with a speed restriction) once engineers had completed a temporary structure over the top of the failed arch to support the track bed.

During this period many trains were diverted via Worcester, Droitwich and Kidderminster.  This caused significant disruption to both passenger and freight services.  Although no trains became derailed because of the partial failure of the structure, the consequences could have been worse had the arch suddenly collapsed.  The RAIB investigation will therefore include a review of the inspection, maintenance and risk management of this structure and others of its type.

Network Rail has been notified of the RAIB^s investigation.

The RAIB^s investigation is independent of any investigations by the safety authority (the Office of Rail Regulation).

The RAIB will publish a report, including any recommendations to improve safety, at the conclusion of its investigation. This report will be available on the RAIB website.