Bookham Tunnel near miss: what every COSS must know
In April 2025, three track workers entered the wrong tunnel at Bookham and were nearly struck by a train at 33 mph. The RAIB found the safe work pack referenced the wrong tunnel. Here is what it means for COSS competence.
On 29 April 2025, a lookout reported a train approaching. Three track workers ran — but they were in the wrong tunnel. The safe work pack named Bookham Tunnel, but the workers were inside the adjacent Leatherhead Tunnel. The train passed at 33 mph with no prior warning.
What went wrong
RAIB Report 07/2026 identified two primary failures. The safe work pack contained an error — it named the wrong tunnel. The COSS did not verify the worksite location against the physical environment before allowing work to begin.
The COSS duty
A COSS is responsible for the safety of every person in their work group. That includes confirming the possession boundary physically matches the paperwork before any worker steps near the line. A document error does not remove that duty — it makes it more important.
Before work begins, a COSS must confirm: possession limits match the physical location; all access and egress points are identified; the work group is briefed on the specific hazards of that exact location.
What managers must watch for
This is a competence failure, not just a paperwork error. The question for any safety manager is: would your COSS have caught this?
COSS competence assessment must test situational awareness and the ability to challenge documentation that does not match observed conditions. A COSS who accepts paperwork without checking the physical environment is a risk to every worker in their group.
GB Rail Training COSS assessments test exactly this — decision-making under real conditions, not just knowledge recall. Managers can track team assessment scores and identify gaps before they become incidents.
Source: RAIB Report 07/2026 — Near miss at Bookham Tunnel, Surrey, 29 April 2025.
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