Editing Channel Tunnel (section)

=== Safety ===
The [[Channel Tunnel Safety Authority]] is responsible for some aspects of safety regulation in the tunnel; it reports to the [[Intergovernmental Commission]] (IGC).<ref>{{cite web |url=http://www.channeltunneligc.co.uk/The-CTSA.html?lang=en |title=The Channel Tunnel Safety Authority |work=Channel Tunnel Intergovernmental Commission |year=2013 |access-date=11 June 2013 |archive-date=22 April 2021 |archive-url=https://web.archive.org/web/20210422081422/https://www.channeltunneligc.co.uk/The-CTSA.html?lang=en |url-status=dead }}</ref>
{{Routemap
|title = Channel Tunnel safety
|collapsible = yes
|legend = no
|map =
CONTg\\~~'''North running tunnel'''
STRg\uCONTg\~~Service tunnel
STRg\uSTR\CONTg~~'''South running tunnel'''
STRg\uSTR\STRf
uXBHF-L\uXBHF-M\uXBHF-R~~Emergency door every {{cvt|375|m|ft}}
CONTf\uCONTf\CONTf
}}
The service tunnel is used for access to technical equipment in cross-passages and equipment rooms, to provide fresh-air ventilation and for emergency evacuation. The Service Tunnel Transport System (STTS) allows fast access to all areas of the tunnel. The service vehicles are rubber-tired with a buried wire guidance system. 

The 24 STTS vehicles are used mainly for maintenance but also for firefighting and emergencies. "Pods" with different purposes, up to a payload of {{convert|2.5|–|5|tonne}}, are inserted into the side of the vehicles. The vehicles cannot turn around within the tunnel and are driven from either end. The maximum speed is {{convert|80|km/h|mi/h|0|abbr=on}} when the steering is locked. A fleet of 15 Light Service Tunnel Vehicles (LADOGS) was introduced to supplement the STTSs. The LADOGS has a short wheelbase with a {{convert|3.4|m|abbr=on|adj=on}} turning circle, allowing two-point turns within the service tunnel. Steering cannot be locked like the STTS vehicles, and maximum speed is {{convert|50|km/h|mi/h|0|abbr=on}}. Pods up to {{convert|1|tonne}} can be loaded onto the rear of the vehicles. Drivers in the tunnel sit on the right, and the vehicles drive on the left. Owing to the risk of French personnel driving on their native right side of the road, sensors in the vehicles alert the driver if the vehicle strays to the right side.<ref name="Kirkland pp.247–254">Kirkland pp. 247–254</ref>

The three tunnels contain {{convert|6000|tonne}} of air that needs to be conditioned for comfort and safety. Air is supplied from [[ventilation (architecture)|ventilation]] buildings at Shakespeare Cliff and Sangatte, with each building capable of providing 100% standby capacity. Supplementary ventilation also exists on either side of the tunnel. In the event of a fire, ventilation is used to keep smoke out of the service tunnel and move smoke in one direction in the main tunnel to give passengers clean air. The tunnel was the first main-line railway tunnel to have special cooling equipment. Heat is generated from traction equipment and drag. The design limit was set at {{convert|30|C|F|sigfig=2}}, using a mechanical cooling system with refrigeration plants on both sides that run chilled water circulating in pipes within the tunnel.<ref name="Kirkland pp.212–230"/>

Trains travelling at high speed create [[piston effect]] pressure changes that can affect passenger comfort, ventilation systems, tunnel doors, fans and the structure of the trains, and which drag on the trains.<ref name="Kirkland pp.212–230">Kirkland pp. 212–230</ref> Piston relief [[Duct (HVAC)|ducts]] of {{cvt|2|m|ftin||adj=on}} diameter were chosen to solve the problem, with 4&nbsp;ducts per kilometre to give close to optimum results. However, this design led to extreme lateral forces on the trains, so a reduction in train speed was required and restrictors were installed in the ducts.<ref name="CT experience">The Channel Tunnel Experience Lessons for the Future pp. 19–23</ref>

The safety issue of a possible fire on a passenger-vehicle shuttle garnered much attention, with Eurotunnel noting that fire was the risk attracting the most attention in a 1994 safety case for three reasons: the opposition of ferry companies to passengers being allowed to remain with their cars; [[Home Office]] statistics indicating that car fires had doubled in ten years; and the long length of the tunnel. Eurotunnel commissioned the UK Fire Research Station—now part of the [[Building Research Establishment]]—to give reports of vehicle fires, and liaised with Kent Fire Brigade to gather vehicle fire statistics over one year. Fire tests took place at the French Mines Research Establishment with a mock wagon used to investigate how cars burned.<ref name="Kirkland pp.231–240">Kirkland pp. 231–240</ref> The wagon door systems are designed to withstand fire inside the wagon for 30&nbsp;minutes, longer than the transit time of 27&nbsp;minutes. Wagon air conditioning units help to purge dangerous fumes from inside the wagon before travel. Each wagon has a fire detection and extinguishing system, with sensing of ions or [[ultraviolet radiation]], smoke and gases that can trigger [[Haloalkane|halon]] gas to quench a fire. 

Since the HGV wagons are not covered, fire sensors are located on the loading wagon and in the tunnel. A {{convert|10|in|adj=on}} water main in the service tunnel provides water to the main tunnels at {{cvt|125|m|ft|0|adj=on}} intervals.<ref>{{cite news | url = http://news.bbc.co.uk/1/hi/uk/7612776.stm | title = Focus turns to cause of tunnel blaze |work=BBC News   | access-date =12 September 2008 | date = 12 September 2008 | first=Andrew | last=McFarlane}}</ref> The ventilation system can control smoke movement. Special arrival sidings accept a train that is on fire, as the train is not allowed to stop whilst on fire in the tunnel unless continuing its journey would lead to a worse outcome. Two STTS (Service Tunnel Transportation System)<ref>{{cite web | url = http://www.eurotunnelgroup.com/uk/the-channel-tunnel/glossary/#s | title = Glossary | access-date = 24 August 2012 | archive-url = https://web.archive.org/web/20120815011501/http://www.eurotunnelgroup.com/uk/the-channel-tunnel/glossary/#s | archive-date = 15 August 2012 | url-status = dead }}</ref> vehicles with firefighting pods are on duty at all times, with a maximum delay of 10&nbsp;minutes before they reach a burning train.<ref name="Kirkland fire"/>
Eurotunnel has banned a wide range of hazardous goods from travelling in the tunnel.