PTS Working in Tunnels — Questions and Answers
Question 1: What is the primary additional hazard when working in a tunnel compared to open track?
- Trains travel faster inside tunnels than on open track
- Escape options are severely restricted and aerodynamic effects from passing trains are amplified (Correct answer)
- Electrified lines are always switched off inside tunnels
- Mobile phones must be used instead of radios inside tunnels
Correct 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.
Question 2: In a tunnel, refuge niches (alcoves set into the tunnel wall) must typically be provided at maximum intervals of:
- 10 metres
- 25 metres (Correct answer)
- 100 metres
- 250 metres
Correct 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.
Question 3: Before entering a tunnel to work, a COSS must:
- Obtain permission from the local council
- Confirm the emergency procedures and refuges, and ensure all workers are briefed on the specific tunnel hazards (Correct answer)
- Disable all lookout warning systems as they are ineffective in tunnels
- Wait until all trains have been suspended on all routes through the tunnel
Correct 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.
Question 4: The aerodynamic pressure wave produced by a train passing through a tunnel is significant because:
- It can extinguish gas-powered lighting used by maintenance teams
- It can knock workers off their feet and cause tools or materials to become projectiles (Correct answer)
- It improves ventilation, reducing heat-related risk for track workers
- It only affects workers within 1 metre of the running rail
Correct 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.
Question 5: If a worker feels unwell or becomes injured while working inside a long tunnel, the FIRST priority is:
- Continue working to avoid delaying the job
- Call the signaller and request the tunnel is cleared of trains, then assist the worker to the nearest refuge or tunnel entrance (Correct answer)
- Send the worker to walk out of the tunnel unaccompanied
- Wait for the next planned train path to pass before evacuating
Correct 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.
Question 6: Which statement about lookout warning systems in tunnels is CORRECT?
- Standard audible horns are always sufficient warning inside any tunnel
- Warning distances may need to be extended inside tunnels because sound travels differently and sight lines are limited (Correct answer)
- Tunnels are always protected by automatic train protection so no lookout is needed
- Lookouts are not required in tunnels shorter than 500 metres
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.
PTS Working in Tunnels
What is the primary additional hazard when working in a tunnel compared to open track?