Press release

Report 20/2015: Unsafe events at Heathrow Tunnel Junction

RAIB has released its report into unsafe events at Heathrow Tunnel Junction, 27 and 28 December 2014.

Yellow engineering trolley underneath the train after the collision (image courtesy of Carillion)

Yellow engineering trolley underneath the train after the collision (image courtesy of Carillion)


On 27 December 2014, and again on 28 December 2014, track workers were at serious risk of being struck by trains at the Stockley Flyover construction site, on the Heathrow Airport branch line. In the second incident, a train did collide with a small trolley which was being placed on the line by track workers.

During the first incident, 14 track workers walked along the open Down Airport line; an area where limited visibility meant that it was unsafe to do this when train services were operating. They mistakenly believed that train services had been stopped. A Heathrow Airport to London service used the line shortly after the workgroup had been warned by other staff and had moved clear. The investigation found that an inappropriate system was used to control access to the track, permitting trains to start operating when track workers could reasonably believe services remained suspended. Staff had also been directed to walk along a line when paperwork showed it was open to traffic.

The following day, two track workers were placing a small trolley on the Up Airport line when a train emerged from a nearby tunnel at a speed of 45 mph (72 km/h). The track workers moved clear of the line seconds before the train struck the trolley. There were no injuries and only minor damage. The track workers believed the line was closed, a consequence of being accustomed to working in a way which differed from the mandated site safety system.

The two incidents, and other safety shortcomings found, showed that site supervision processes had not identified that deviation from the mandated site safety system had become normal practice. Also, formalised briefings had not been supplemented by any site signage to increase the likelihood of staff being aware of which lines were open.


RAIB has made four recommendations, all addressed to Network Rail with some also seeking input from major contractors. The first seeks an improvement in monitoring of railway safety arrangements on major construction site. The second relates to effective monitoring of staff controlling access to worksites. The third seeks to provide workers on major construction sites with additional sources of information about the lines on which it is safe to work. The final recommendation seeks a review, and if necessary improvement, of the railway access control systems used on large construction sites.

Three learning points are included to remind engineering supervisors and COSSs that they should comply with safety requirements and query any safety related anomalies in their paperwork. There are two other learning points made which are not directly related to the incidents: a reminder to employers that they should ensure that their staff have received railway rule book updates; and a reminder to those preparing site safety paperwork to make it comprehensive, but concise.

Notes to editors

  1. The sole purpose of RAIB investigations is to prevent future accidents and incidents and improve railway safety. RAIB does not establish blame, liability or carry out prosecutions.

  2. RAIB operates, as far as possible, in an open and transparent manner. While our investigations are completely independent of the railway industry, we do maintain close liaison with railway companies and if we discover matters that may affect the safety of the railway, we make sure that information about them is circulated to the right people as soon as possible, and certainly long before publication of our final report.

  3. For media enquiries, please call 020 7944 3108.

Newsdate: 16 December 2015


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Published 16 December 2015