A '''Controller of Site Safety''' or '''COSS''' is a person qualified by the British civil engineering company Network Rail to ensure safe practice for work occurring on or near railway tracks and infrastructure. Their primary role is to set up a 'safe system of work' (SSOW) to protect staff working on or near tracks from trains.

==History== {{Quote box |quote = The PICOW is responsible for taking charge of the arrangements to ensure that you and anyone else in the group, is '''NOT''' put in a position of danger from approaching trains or movements. |source = ''Rule Book No. 2'' (1998)<ref>{{cite book |last1=Railtrack |title=GO/RT3002 - Personalised Rule Book No. 2 - Extracts from the Rule Book - Sections A, B(i) To B(iii), C, F, S and T(ii) |date=February 1996 |publisher=Railtrack |location=London}}</ref> |align = right |width = 300px }} The British Rail Rule Book assigned responsibility for appointment of lookouts for warning railway staff of approaching trains to the 'man-in-charge' through the 1980s.<ref name="rulebook1972">{{cite book |title=Rule Book - BR 87109 |date=October 1972 |publisher=British Railways Board |location=London |chapter=Section P - Safety of Men working on or about the line - Appointment of Lookoutmen}}</ref><ref name="rulebook1950">{{cite book |title=Rule Book 1950 - (1961 Amended Reprint) |date=1961 |publisher=The Railway Clearing House |location=London |pages=275–276 |chapter=Rule 234(d) - Appointment of Look-out Men}}</ref><ref name="1988BR12323/8">{{cite book |title=Track Safety Handbook - BR 12323/8 |date=1988 |publisher=British Railways Board |location=London}}</ref> In February 1985, four railway workers that were part of a six-man crew clearing snow from points were struck and killed by a passing train.<ref name="vaughan">{{cite book |last1=Vaughan |first1=Adrian |title=Tracks To Disaster |date=2000 |publisher=Ian Allan Publishing |location=Surrey, UK |isbn=0711027315 |pages=40–43 |chapter=Severn Tunnel Junction: 11 February 1985}}</ref> The group had no defined leader and no appointed lookouts despite poor visibility due to falling snow. In 1989, the role was renamed "Person In Charge of Work" (PICOW), but otherwise remained similar to the previous role.<ref name="1989BR12323/8">{{cite book |title=Track Safety Handbook - BR 12323/8 |date=June 1989 |publisher=British Railways Board |location=London}}</ref>

In 1990, eleven railway staff were killed by trains while on or about the tracks, combined with further fatalities in 1991, British Rail revised the rules surrounding staff on or about the tracks, implementing significant changes in response to deficiencies in the rule book at the time.<ref name="railwaysafety92">{{cite book |last1=Health & Safety Executive |last2=The Department of Transport |title=Railway Safety - Report on the safety record of the railways in Great Britain during 1991/92 |date=1992 |publisher=Her Majesty's Stationery Office |isbn=0118863908}}</ref>

From April 1992, a PICOW was required to be appointed anytime workers were on or near the line, in response to these incidents, tasked with ensuring workers are kept safe from trains by appointing lookouts, arranging closure of tracks and other methods.<ref name="1992BR12323/8">{{cite book |title=Track Safety Handbook 1992 - BR 12323/8 |date=April 1992 |publisher=British Railways Board}}</ref> Additionally, the PICOW role now required a formal certification to perform, with a formal training course to teach key concepts, such as setting up safe system of work and usage of railway documents to plan work.<ref name="1992BR12323/8"/> The course was a 2-day course, implemented on the job experience requirements before someone could become eligible to train as a PICOW.<ref name="CECESM Part C.1">{{cite web |title=CECESM Part C.1 - Training and Certification of Lookouts and PICOW |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/CECESM-Part-C1 |website=rssb.co.uk |publisher=British Rail Board |access-date=21 September 2025 |date=February 1992 |url-access=registration}}</ref><ref name="GHZT0022 Issue 1">{{cite web |title=GHZT0022 Issue 1 - Competency in PICOW Rules |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/GHZT0022-Iss-1 |website=rssb.co.uk |publisher=British Rail Board |access-date=21 September 2025 |date=January 1994 |url-access=registration}}</ref>

On 7 August 1999, this job role was officially renamed to Controller of Site Safety (COSS).<ref name="rt3170issue1">{{cite book |last1=Railtrack |author1-link=Railtrack |title=RT3170 Issue 1 - Personal Track Safety Handbook |date=1 April 1998 |publisher=Railtrack |edition=First}} (This was part of a loose erratum page provided with the handbook, but was not printed within the original handbook itself.)</ref><ref>Railtrack. (August 1999). ''August 1999 Periodical Operating Notice'' Railtrack.</ref>

==Job role== The COSS has responsibility for the safety of themselves and the group under their direction and could be subject to prosecution should someone be killed or injured by their negligence.<ref>{{cite web |title=Supervisor charged in rail worker's death |url=http://news.bbc.co.uk/2/hi/uk_news/england/2519447.stm |website=BBC |publisher=British Broadcasting Corporation |access-date=4 November 2025 |archive-url=https://web.archive.org/web/20251104200713/http://news.bbc.co.uk/2/hi/uk_news/england/2519447.stm |archive-date=4 November 2025 |date=27 November 2002}}</ref>

The rules around performing the role of a COSS are stated in the Rule Book, a set of documents issued to track staff detailing their duties. Since 2010, this has been Rule Book Handbook 7, ''General duties of a controller of site safety (COSS)''.<ref name="hb7iss10"/>

To become a COSS, someone should have served a suitable period of time on the railways and undertake a five-day course. This is then followed by a period of mentoring by an experienced COSS and then independent regular assessments to ensure that the subject is competent to undertake their role safely and effectively.

A COSS is required to distinguish themselves on site by wearing a blue armlet/badge on the left arm or upper body on which the word "COSS" is printed in white text. They are prohibited from wearing this armlet/badge when not acting as a COSS.<ref name="hb7iss10"/>

===Planning=== Depending on the work, a COSS may be provided with a preplanned safe system of work. However, in situations where work was not planned, such as unexpected signal or track faults, the COSS will need to decide on and implement a safe system of work themselves.<ref name="coss handbook2005">{{cite web |title=COSS Handbook |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/RS502-Iss-1 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=22 September 2025 |date=February 2005 |url-access=registration}}</ref> Further, a COSS may need to adapt a previously planned safe system of work if conditions change, such as weather, time of day or the location of the work.<ref name="GERT8000-T7 Iss 3"/><ref name="coss handbook2005"/>

Prior to approaching the railway line to start work, the COSS must be confident that the safe system of work will be adequate to protect the entire group from approaching trains. This includes factoring in variable conditions such as time of day, weather conditions, track and landscape geography and the nature of the work itself.<ref name="GERT8000-T7 Iss 3"/> They are also required to document that they've considered these factors and the decisions made regarding the safe system of work and if there were changes from previously planned arrangements.<ref name="GERT8000-T7 Iss 3"/>

The COSS also has the power to arrange for a railway track to be 'blocked' or closed to train traffic to enable work to be performed.<ref name="HB8 iss10">{{cite web |title=GERT8000-HB8 Issue 10 - IWA, COSS or PC blocking a line |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/gert8000-hb8-iss-10 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=22 September 2025 |date=July 2024}}</ref><ref name="coss handbook2005"/> The COSS has to coordinate this with the signaller, place detonators and possession limit board.{{efn|A portable double-sided stop sign that has a red light, which denotes the limit of a track blockage for engineering work.<ref name="GERT8000-T7 Iss 3"/>}}<ref name="HB8 iss10"/>

===Briefing=== Prior to starting work near or on the tracks, the COSS must give the group they are in charge of a safety briefing that explains the following:<ref name="hb7iss10">{{cite web |title=GERT8000-HB7 Issue 10 - General duties of a controller of site safety (COSS) |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/gert8000-hb7-iss-10 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=20 September 2025 |date=12 June 2025|url-access=registration}}</ref><ref name="coss handbook2005"/> {{columns-list|colwidth=20em| * Work being carried out * Location work is being carried out * The status of tracks: which are open to trains and which are closed to trains * The safe system of work * The location of the position of safety * If using site wardens, who they are and limits of the safe working area * If using lookouts, who they are and how they will give warning * Any other hazards or information the group should know about, such as the presence overhead line equipment/conductor rail, limited clearances or poor walking conditions * Means of communication in an emergency }} Prior to accessing the tracks, the COSS must also verify that all members of the group have valid Sentinel competency card.{{efn|A photo ID card that lists railway related qualifications, and proves an individual is trained and permitted to be on or near the tracks.}} All members of the group are also required to sign the safe-work briefing form to confirm they understood the information in the briefing.<ref name="hb7iss10"/> The COSS is required to have direct supervision of the group, and must remain with them while on or near the tracks.<ref name="hb7iss10"/>

The preferred safe systems of working where the staff are protected from line open to train movements, either by blocking some or all lines to traffic or controlling the distance the group is from the track (called Safeguarded/Fenced/Separated areas in order of consideration). This method was formerly called a Green Zone. This is the safest way of working due to the higher risks with trains moving at speed, although many incidents still happen within blocks.

Open Line working (formerly known as Red Zone) means the lines are open to train movements; this is seen as more risky than Safeguarded/Fenced/Separated areas, and is avoided in the rail industry where practicable.

==Safe System of Work== A Safe System of Work (SSOW) is the method that railway employees use to protect themselves from being struck by moving trains while working on or near train tracks. {| class="wikitable" ! Hierarchy{{efn|Discontinued after 2010<ref name="tranche2"/>}} !! Name<ref name="GERT8000-T7 Iss 3"/> !! Type{{efn|Discontinued after 2010<ref name="tranche2"/>}} !! Description !! Other notes |- | 1 || Safeguarded || Green zone || All tracks are closed to trains, including parallel tracks where work isn't occurring || Engineering trains and equipment moving at approximately {{convert|5|mph|kph}} are permitted |- | 2 || Fenced || Green zone || A rigid barrier, plastic construction fencing or barricade tape prevents workers from exiting the area where tracks are closed and entering an open track<ref name="GERT8000-T7 Iss 3"/> || |- | 3 || Separated || Green zone || A gap of {{convert|2|m|ft}} between the edge of the safe working area and an open line is maintained with a site warden{{efn|A worker tasked with observing the boundary between the safe working area and the open tracks, and warning any worker who attempts to leave the safe working area to return to it.}} appointed<ref name="GERT8000-T7 Iss 3"/> || |- | 4 || ATWS || Red zone || Warning to workers is given by lights and alarm tone of an Automatic Track Warning System (ATWS)<ref name="GERT8000-T7 Iss 3"/> || ATWS systems can be temporary or permanently installed and operates automatically when turned on. |- | 5 || TOWS || Red zone ||Warning given by alarm tone of Train Operated Warning System (TOWS)<ref name="GERT8000-T7 Iss 3"/> || A British Rail designed, permanently installed, warning system that gives off an audible alarm tone with 25 seconds of warning, based on track circuits. |- | {{n/a}}{{efn|SATWS was introduced after the discontinuation of the Hierarchy.}} || SATWS || {{n/a}}{{efn|SATWS was introduced after the discontinuation of Red/Green working terms.}} || Warning given by sound and lights of a Semi-automatic track warning system (SATWS) that is automatically activated by a train, but must be manually cancelled by a staff member after the train passes<ref name="HB1 iss9">{{cite web |title=GERT8000-HB1 Issue 9 - General duties and track safety for track workers |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/gert8000-hb1-iss-9 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=22 September 2025 |date=June 2025}}</ref> || Unlike ATWS or TOWS, a human must deactivate the warning after the train has passed.<br>Unlike LOWS, the system automatically detects a train. |- | 6 || LOWS || Red zone || Warning given by sound and/or lights of a portable Lookout Operated Warning System (LOWS) device at work site operated by a human positioned to watch for trains away from the work site<ref name="GERT8000-T7 Iss 3"/> || Unlike ATWS, a human must initiate the warning of a train approaching. |- | 7 || Lookout || Red zone || Warning is given by a human lookout at the work site, typically by sound of a horn or whistle<ref name="GERT8000-T7 Iss 3"/> || Also referred to as 'unassisted lookout' in newer documentation |} Prior to 2010, these systems were referred to and grouped as 'green zone' and 'red zone'.<ref name="GERT8000-T7 Iss 3">{{cite web |title=GERT8000-T7 Issue 3 - Safe systems of work when walking or working on or near the line |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/GERT8000-T7-Iss-3 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=20 September 2025 |date=10 July 2006|url-access=registration}}</ref> Green zone referred to systems where the work site was protected from trains by closing the track{{efn|Except to slow moving engineering trains and equipment}} and red zone referred to systems where the tracks were still open to trains and workers would be required to move to a position of safety when trains approached.<ref name="GERT8000-T7 Iss 3"/> In an effort to reduce confusion and simplify the rule book, the terms were phased out in 2010.<ref name="tranche2">{{cite web |title=Explanation of Change - New Approach to the Rule Book - Tranche 2 |url=https://www.rssb.co.uk/-/media/Project/RSSB/RssbWebsite/Documents/Registered/Impact-Assessments/2020/09/16/10/23/10-EOC02.pdf |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=20 September 2025 |date=September 2010|url-access=registration}}</ref> The hierarchy was also removed at this time, as it was largely rendered moot by instructions that required that the SSOW selected be most suitable to the task, circumstances and location of work.<ref name="tranche2"/>

Network Rail has aimed to eliminate the usage of human lookouts, with a significant push occurring after an incident at Margam, where two track workers were struck and killed by a train.<ref name="horgan2021">{{cite web |last1=Horgan |first1=Rob |title=Network Rail to replace all human lookouts following rail worker death in London |url=https://www.newcivilengineer.com/latest/network-rail-to-replace-all-human-lookouts-following-rail-worker-death-in-london-15-06-2021 |website=newcivilengineer.com |publisher=New Civil Engineer |access-date=20 September 2025 |date=15 June 2021}}</ref> At Margam, the six person crew had split into two groups, and the appointed lookout had remained with the other group.<ref>{{cite web |last1=Rail Accident Investigation Board |title=Rail Accident Report - Track workers struck by a train at Margam, Neath Port Talbot - 3 July 2019 |url=https://assets.publishing.service.gov.uk/media/5fabd9c9e90e075c4965171e/R112020_201112_Margam.pdf |publisher=Government of the United Kingdom |access-date=20 September 2025 |date=November 2020}}</ref> A 2021 fatality near Surbiton station prompted Network Rail to accelerate these efforts.<ref>{{cite web |last1=Rail Accident Investigation Board |title=Rail Accident Report - Track worker struck by a train near Surbiton station, south-west London - 9 February 2021 |url=https://assets.publishing.service.gov.uk/media/628cd27fd3bf7f1f45380351/R052022_220525_Surbiton.pdf |publisher=Government of the United Kingdom |access-date=20 September 2025 |date=May 2022}}</ref> In the June 2022 Network Rail Board meeting, it was acknowledged that lookout usage was already low as practical, with the majority of routes not using human lookouts. Total elimination was not realistic.<ref name="horgan2022">{{cite web |last1=Horgan |first1=Rob |title=Network Rail cuts number of human lookouts 'as low as reasonably practicable' |url=https://www.newcivilengineer.com/latest/network-rail-cuts-number-of-human-lookouts-as-low-as-reasonably-practicable-17-11-2022 |website=newcivilengineer.com |publisher=New Civil Engineer |access-date=20 September 2025 |date=17 November 2022}}</ref><ref name="june2022minutes">{{cite web |last1=Network Rail |title=Minutes of a meeting of the Board held on Thursday 30 June 2022 |url=https://www.networkrail.co.uk/wp-content/uploads/2022/11/Board-minutes-30-June-2022.pdf |website=networkrail.co.uk |publisher=Network Rail Limited |access-date=20 September 2025 |archive-url=https://web.archive.org/web/20240117034600/https://www.networkrail.co.uk/wp-content/uploads/2022/11/Board-minutes-30-June-2022.pdf |archive-date=17 January 2024 |date=30 June 2022}}</ref>

In 2025, the Rail Safety and Standards Board introduced updates to the Rule Book to further restrict the usage of lookouts. From December 2025, lookouts are only allowed when no other safe system of work is suitable, can not be used at night, during poor visibility or in/near tunnels.<ref name="hb3iss4"/> Further train speeds must be under 25&nbsp;mph (40&nbsp;km/h), and there are no junctions that would allow the train to unexpectedly change tracks.<ref name="hb3iss4"/> The usage of intermediate and distant lookouts{{efn|In situations where visibility is limited, such as near curves, distant and intermediate lookouts could be positioned to signal the lookout at the worksite of an approaching train.<ref name="hb3iss3">{{cite web |title=GERT8000-HB3 Issue 3 - Duties of the lookout and site warden |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/GERT8000-HB3-Iss-3 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=20 September 2025 |date=9 June 2014|url-access=registration}}</ref>}} was also banned.<ref name="hb3iss4">{{cite web |title=GERT8000-HB3 Issue 4 - Duties of the lookout and site warden |url=https://www.rssb.co.uk/standards-catalogue/CatalogueItem/gert8000-hb3-iss-4 |website=rssb.co.uk |publisher=Rail Safety & Standards Board |access-date=20 September 2025 |date=9 June 2025|url-access=registration}}</ref><ref name="hb7iss10"/>

==Notes== {{notelist}}

==References== {{reflist}}

==External links== * [https://info.railsentinel.co.uk/ Sentinel]

{{DEFAULTSORT:Controller Of Site Safety}} Category:Railway safety Category:Railway occupations