separate the driver from the rear passengers. Protection line The armoured "Protection Line" vehicles were built from 2000 to 2001 and were based on the 740iL and 750iL models. Security features include body armor, bullet-resistant glass and run-flat tyres. An intercom system is provided to communicate with people outside the vehicle while the windows and doors are shut. Security line A High-Security version with protection up to B6/7 was also available in Europe, known internally as the 750iL S. The additional security measures brought an additional weight of compared to the normal 750iL. Features include explosive cord around the windshield allowing removal of the windshield facilitating escape and hydraulically actuated windows. A gas sensor can detect irritants like CS gas and respond by turning the blower motor off, closing fresh air flaps and all windows. A fire suppression system is triggered by either a button or the detection of extreme temperatures in the engine bay or the vicinity of the fuel tank. A breathing air system is also available which delivers air from a cylinder in the trunk, up to three firearms cases designed to fit a Heckler & Koch MP5K were also optionally available as well as spherical gunports in the doors. 750hL On 11 May 2000, BMW presented a fleet of fifteen 750hL's in Berlin. Its twelve-cylinder hydrogen combustion engine can be operated on both hydrogen and petrol. In operation on hydrogen, it delivers , accelerating from 0 to in 9.6 seconds and slowing the car to attain a top speed of . The production of the hydrogen engine was integrated into the regular engine production at the Dingolfing plant. It differs from the conventional petrol engine essentially only in regards to the intake tract with additional injection valves for hydrogen. The hydrogen is stored cryogenically at a temperature of minus 253 degrees Celsius in a double-walled steel tank behind the rear seat back. The hydrogen tank holds 140 litres and allows an additional range of . In addition, the 750hL has a fuel cell rated at at 42 volts. This is not used as a drive unit, but as an auxiliary power unit (APU) for power supply to the electrical system. During the Expo 2000 in Hanover the vehicles were used as shuttles. From February to November 2001 the vehicles were part of the "CleanEnergy WorldTour 2001" in the cities of Dubai, Brussels, Milan, Tokyo, Los Angeles