Working in Tunnels Flashcards

What is the primary additional hazard when working in a tunnel compared to open track?

Answer: Escape options are severely restricted and aerodynamic effects from passing trains are amplified

In a tunnel, workers cannot step well clear of the track as they might in the open — escape is limited to designated refuges. Aerodynamic pressure waves from passing trains are also far stronger inside tunnels, posing a risk of being knocked over or struck by debris even from a train passing through a neighbouring tunnel.

In a tunnel, refuge niches (alcoves set into the tunnel wall) must typically be provided at maximum intervals of:

Answer: 25 metres

Network Rail standards require refuge niches at a maximum of every 25 metres in tunnels. This ensures a worker never has to travel more than 12.5 metres to reach a place of safety when a train approaches. The 25-metre interval is a core piece of tunnel safety knowledge tested in PTS.

Before entering a tunnel to work, a COSS must:

Answer: Confirm the emergency procedures and refuges, and ensure all workers are briefed on the specific tunnel hazards

Prior to tunnel entry, the COSS must confirm the location of all refuges, communicate emergency evacuation procedures specific to that tunnel, and brief all workers on the amplified aerodynamic effects and limited escape routes. Standard open-track briefings are insufficient for tunnel environments.

The aerodynamic pressure wave produced by a train passing through a tunnel is significant because:

Answer: It can knock workers off their feet and cause tools or materials to become projectiles

The pressure wave (also called the 'piston effect') generated by a train in a tunnel can be powerful enough to knock a person over and turn unsecured equipment into dangerous projectiles. Workers must be in a refuge before the train enters the tunnel — being adjacent to a niche when the train arrives is insufficient.

If a worker feels unwell or becomes injured while working inside a long tunnel, the FIRST priority is:

Answer: Call the signaller and request the tunnel is cleared of trains, then assist the worker to the nearest refuge or tunnel entrance

Worker welfare and safety take absolute precedence. The COSS should immediately contact the signaller to protect the worker, then assist or arrange assistance to the nearest refuge or exit. Leaving an injured or unwell worker unaccompanied in a tunnel, or delaying action until a train passes, is not acceptable.

Which statement about lookout warning systems in tunnels is CORRECT?

Answer: Warning distances may need to be extended inside tunnels because sound travels differently and sight lines are limited

Tunnels distort and amplify sound in unpredictable ways, and curved tunnels eliminate line-of-sight sighting distances. Both factors can reduce the effectiveness of standard warning methods, potentially requiring additional or enhanced warning arrangements as specified in the site-specific safe system of work.