<P> 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 - tyred with a buried wire guidance system . The 24 STTS vehicles are used mainly for maintenance but also for firefighting and in emergencies . "Pods" with different purposes, up to a payload of 2.5--5 t (2.8--5.5 tons), 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 80 km / h (50 mph) when the steering is locked . A fleet of 15 Light Service Tunnel Vehicles (LADOGS) was introduced to supplement the STTSs . The LADOGS have a short wheelbase with a 3.4 m (11 ft) turning circle, allowing two - point turns within the service tunnel . Steering cannot be locked like the STTS vehicles, and maximum speed is 50 km / h (31 mph). Pods up to 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 . </P> <P> The three tunnels contain 6,000 tonnes (6,600 tons) of air that needs to be conditioned for comfort and safety . Air is supplied from 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 30 ° C (86 ° F), using a mechanical cooling system with refrigeration plants on both sides that run chilled water circulating in pipes within the tunnel . </P> <P> 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 . Piston relief ducts of 2 - metre (7 ft) diameter were chosen to solve the problem, with 4 ducts per kilometre to give close to optimum results . Unfortunately this design led to unacceptable lateral forces on the trains so a reduction in train speed was required and restrictors were installed in the ducts . </P> <P> 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 . The wagon door systems are designed to withstand fire inside the wagon for 30 minutes, longer than the transit time of 27 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 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 10 - inch (250 mm) water main in the service tunnel provides water to the main tunnels at 125 - metre (410 ft) intervals . 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 . Eurotunnel has banned a wide range of hazardous goods from travelling in the tunnel . Two STTS (Service Tunnel Transportation System) vehicles with firefighting pods are on duty at all times, with a maximum delay of 10 minutes before they reach a burning train . </P>

Who gained control of the channel of water between england and france and the north sea