PTS PTS - Personal Track Safety COSS Roles and Responsibilities 2 — Questions and Answers
Question 1: What is the maximum number of workers that a COSS can directly control on a railway worksite?
- There is no limit — a COSS can control any number of workers
- The number is determined by the nature of the work, the site conditions, and the risk assessment — but a COSS must always be able to directly supervise and communicate with all workers under their control (Correct answer)
- A COSS can control a maximum of 10 workers at any time
- A COSS can control up to 20 workers on any site
Correct answer: The number is determined by the nature of the work, the site conditions, and the risk assessment — but a COSS must always be able to directly supervise and communicate with all workers under their control
There is no fixed numerical limit, but the COSS must be able to directly supervise and communicate with every worker under their control — site conditions and risk assessment determine the effective maximum.
The Network Rail Rule Book does not specify a fixed maximum number of workers per COSS, but places an overriding requirement that the COSS must be able to directly supervise, communicate with, and be responsible for all workers under their control at all times. In practice, this means the effective maximum varies with site complexity, visibility, terrain, noise levels, and the nature of work. On a simple cess inspection, a COSS might manage 10 workers. In a complex multi-track environment with heavy machinery, 4-5 workers might be the practical limit. The COSS must refuse to take on more workers than they can safely manage.
Question 2: What happens to the COSS's responsibilities when they temporarily hand over control of the site to another COSS?
- Responsibility transfers fully and immediately on verbal agreement
- A formal documented handover must take place, including briefing the incoming COSS on all hazards, protections, and workers — responsibility only transfers once the handover is complete and confirmed (Correct answer)
- The outgoing COSS retains legal responsibility regardless of handover
- Handovers can only happen at the start of a new shift, not mid-shift
Correct answer: A formal documented handover must take place, including briefing the incoming COSS on all hazards, protections, and workers — responsibility only transfers once the handover is complete and confirmed
COSS handovers must be formal and documented — the incoming COSS must be fully briefed on all hazards, protections, safe working limits, and workers before taking over responsibility.
A COSS handover is a safety-critical activity. The outgoing COSS must formally brief the incoming COSS on: all workers present and their positions; the nature and status of all protection arrangements (blockages, possessions); safe working limits and any changes during the shift; all hazards identified in the risk assessment and any new ones identified during work; the status of any ongoing tasks; and the communication arrangements with the signaller. A handover record should be made. Responsibility transfers to the incoming COSS only when they confirm they have understood the full briefing. Incomplete handovers have contributed to accidents — a rushed or verbal-only handover is inadequate.
Question 3: What is the COSS's duty if they believe the site conditions make the planned safe system of work no longer adequate?
- Continue work but document the concern and submit it to the safety manager later
- Immediately suspend work, withdraw workers to a position of safety, and not resume until a revised safe system of work is in place and agreed with the relevant authority (Correct answer)
- Carry on and rely on workers' experience and awareness to manage the additional risk
- Reduce the working area and continue with fewer workers
Correct answer: Immediately suspend work, withdraw workers to a position of safety, and not resume until a revised safe system of work is in place and agreed with the relevant authority
If site conditions render the safe system of work inadequate, the COSS must immediately suspend work and withdraw workers — work must not resume until a revised, adequate safe system is in place.
The COSS has an overriding duty of care for the safety of all workers under their control. This duty overrides all programme, commercial, or productivity pressures. If conditions change (unexpected train movements, changed weather, equipment failure, newly discovered hazards) and the COSS forms the view that the current safe system of work is no longer adequate, they must immediately suspend work and withdraw workers. The COSS should document the situation, notify the Principal Contractor, and work with the ES and planning team to develop a revised safe system of work. No pressure from managers or clients can legally compel a COSS to resume unsafe work.
Question 4: What must a COSS do when a worker refuses to follow a safety instruction given during the site brief?
- Allow the worker to work in their preferred way as long as they accept personal responsibility
- Do not allow the non-compliant worker to access the track — workers who refuse to comply with safety instructions must be removed from the site (Correct answer)
- Issue a warning but allow work to continue to avoid disrupting the programme
- Consult with other workers about whether the instruction is reasonable
Correct answer: Do not allow the non-compliant worker to access the track — workers who refuse to comply with safety instructions must be removed from the site
A worker who refuses to comply with safety instructions must not be allowed onto the track. The COSS cannot permit access to workers who will not follow the safe system of work.
The safe system of work established by the COSS depends on every worker following the defined procedures. A worker who refuses to comply — whether refusing to wear PPE, ignoring withdrawal procedures, or dismissing safe working limits — creates an unacceptable risk for themselves and all other workers. The COSS must not allow such a worker onto the track. The worker must be told clearly that their access is denied due to non-compliance, and the matter must be reported to the employer. This is not a disciplinary decision by the COSS — it is a safety management action. The COSS has the authority and duty to exclude non-compliant workers.
Question 5: What ongoing record-keeping responsibilities does a COSS have during a work shift?
- Record-keeping is optional — verbal briefing is sufficient for small sites
- The COSS must maintain a site record including workers present, protection arrangements obtained and surrendered, key communications with the signaller, and any safety events or changes to the safe system of work (Correct answer)
- Records are only required for shifts longer than 4 hours
- Only the Principal Contractor is responsible for site records — the COSS has no documentation duty
Correct answer: The COSS must maintain a site record including workers present, protection arrangements obtained and surrendered, key communications with the signaller, and any safety events or changes to the safe system of work
The COSS must maintain a contemporaneous site record of workers, protections obtained and surrendered, signaller communications, and any safety events — this provides an audit trail and supports incident investigation.
The COSS's site record (often called the COSS workbook or site record) is a contemporaneous written log maintained throughout the shift. It must record: all workers present with Sentinel numbers verified; protection arrangements obtained and surrendered with times and signaller names; any changes to the safe system of work; safety events (near misses, injuries, dangerous occurrences); and communications with the ES or signaller that affect the protection or safe working limits. This record provides an audit trail for compliance checking and is invaluable for incident investigation. Maintaining accurate records is a COSS competency requirement under the Network Rail Rule Book.
Question 6: What is the COSS's responsibility regarding workers' fitness to work at the start of a shift?
- Fitness is the sole responsibility of the worker — the COSS need not assess it
- The COSS must carry out a visual and verbal assessment of each worker's fitness at the start of the shift and must not allow any worker who appears unfit onto the track (Correct answer)
- Fitness checks are only required for workers who have been absent due to illness
- The COSS only checks fitness if a worker self-declares a problem
Correct answer: The COSS must carry out a visual and verbal assessment of each worker's fitness at the start of the shift and must not allow any worker who appears unfit onto the track
The COSS must carry out a fitness assessment of all workers at the start of each shift — any worker appearing unfit (intoxicated, unwell, or impaired) must be denied access to the track.
As part of the pre-work briefing, the COSS must make a fitness-to-work assessment for each worker. This includes: observing for signs of alcohol or drug impairment (slurred speech, unsteadiness, unusual behaviour, smell of alcohol); asking workers to confirm they are fit, not taking impairing medication, and have had adequate rest; and considering any disclosed medical conditions. If a worker appears or is confirmed to be unfit, they must not be allowed track access. The COSS is not a doctor — they cannot diagnose conditions — but they have a duty to exercise judgement and exclude workers who appear unfit. This is a fundamental COSS competency under the Sentinel scheme.
PTS PTS - Personal Track Safety COSS Roles and Responsibilities 2
What is the maximum number of workers that a COSS can directly control on a railway worksite?