Controller of Site Safety (COSS) — Sentinel (Network Rail/NSAR, UK) Vocabulary Game
Exam terms with clues and explanations by OpenExamPrep.
About the Controller of Site Safety (COSS) — Sentinel (Network Rail/NSAR, UK) Vocabulary Game
A free word game for the Controller of Site Safety (COSS) — Sentinel (Network Rail/NSAR, UK) exam. Each round shows a clue for one of 20 exam terms across 8 topics. Recall the term, spell it out, then read a short explanation. Rounds pick a random term, so you can keep playing as long as you like.
How to Play
- 1Read the clue and type a term with the right number of letters (3 to 6). Abbreviations count: type the letters only.
- 2Press Check Answer or Enter. Each letter changes color to show how close you are.
- 3You have 6 tries. Stuck? Need a hint? asks the AI tutor for a nudge without giving the term away, and Skip moves to a new term.
- 4After the round, read the explanation, ask the AI to explain it, share your result, or press Next.
- ARight letter, right spot
- AIn the term, wrong spot
- ANot in the term
Topics in the Controller of Site Safety (COSS) — Sentinel (Network Rail/NSAR, UK) Vocabulary Game
Task planning
Rule Book handbooks
Line blockages and protection
Operational messages
Traction power
Site sentries
Incident response
Human factors
Sources for these terms (13)
- Jargon Buster – Safety Central · Source checked 2026-11-04
- Frequently Asked Questions (FAQ's) on Issue 12 of the standard and modules · Source checked 2026-11-04
- NR/L2/OHS/019 Simplification – Issue 12 Standard Change Briefing · Source checked 2026-11-04
- COSS Pre-course Workbook (Manager), Issue 29.5 · Source checked 2026-11-04
- Sentinel – Safety Central · Source checked 2026-11-04
- SAI25 FAQs – Update October 2026 v9.0 · Source checked 2026-11-04
- Reminder of Live Exposed (RoLE) Equipment – Safety Central · Source checked 2026-11-04
- Third rail – Network Rail · Source checked 2026-11-04
- GSM-R: the railway’s mobile communication system – Network Rail · Source checked 2026-11-04
- Safety Alert NRX22-01: Lookout Operated Warning System Incident · Source checked 2026-11-04
- Application of the Electrical Lifesaving Rules · Source checked 2026-11-04
- Deviation Certificate 22-011: Track Circuit Operating Devices · Source checked 2026-11-04
- NR/L2/OHS/019 Issue 13: Safety of people at work on or near the line (06 December 2025) · Source checked 2026-11-04
About the COSS Exam
The Controller of Site Safety (COSS) certification under the Network Rail Sentinel scheme qualifies rail workers to establish and maintain a Safe System of Work (SSOW) for workgroups on or near line. This 100-question practice set covers SSOW planning, GE/RT8000 Rule Book handbooks, line blockages, electrical permits (OLE/DC), lookout working, emergency protection, and Non-Technical Skills (NTS).
Exam sponsor: Network Rail (Sentinel scheme); training assured by NSAR. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.
Assessment
Question count not published by the exam provider
Time Limit
Self-paced study
Passing Score
Not published
Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.
Frequently Asked Questions
Is the COSS vocabulary game free?
Yes. The game is free to play with no sign-up. Signing in adds AI explanations for any term.
How does the COSS vocabulary game work?
Each round shows a clue for one of 20 COSS terms. Guess the term in six tries: green means the right letter in the right spot, yellow means the letter is in the term but in another spot, and gray means it is not in the term. After the round, read the explanation and play the next term.
Where do the COSS terms come from?
OpenExamPrep researched each term from the Network Rail (Sentinel scheme); training assured by NSAR content outline and primary sources, listed under Sources on this page. The game is independent study material, not an official exam resource.
What is a Controller of Site Safety (COSS)?
A COSS is a qualified person certified under the Network Rail Sentinel scheme responsible for setting up and maintaining a Safe System of Work (SSOW) to protect staff working on or near the line from train movements.
What prerequisites are needed for COSS training?
Candidates must hold a valid Sentinel card with Personal Track Safety (PTS) competence, pass a Network Rail medical and drug & alcohol screen, and meet employer experience requirements.