been several dubious claims with undisclosed information. However, the "di pietro" engine has been partially tested with CAD and finite element analysis program and published in scientific papers by Jarosław Zwierzchowski from Lodz University of Technology in 2017, which is an eccentric shaft vane motor that uses low air pressure. Liquidpiston Another recent engine that could be adapted to compressed air is Liquidpiston rotary engine. Compressed air tanks and collision safety The tanks must be designed to safety standards appropriate for a pressure vessel, such as ISO 11439. The pressure vessels or air storage tanks that can be used in compressed air vehicles can be made of low pressure (9 atm) or high pressure (+240 atm), and can be made of composite materials like thermoplastic and fiber reinforced thermoplastics, that means that the price can drop by using recycled or biobased thermoplastics using rotational molding and they are much lighter than lithium-iron batteries and 70% lighter compared to steel tanks, also they have more lifespan and don't need much maintenance. To reduce vehicle weight further the air tanks can be used as structural storage so the tank is the main part of the vehicle chassis while using appropriate impact isolation, however fiber reinforced thermoplastic tanks only have ruptures in case of collision and don't explode. The advance in pressure vessels for vehicles have been developed for hydrogen vehicles with high compression pressure vessels, this is a quote from the hyundai webpage which have created the Hyundai Nexus with 700 atm tanks and favourable crash tests.” Hydrogen tanks require ‘High Strength’ to prevent rupture and ‘High Stiffness’ for durability. Strength is defined as the level of resistance to an influence of an external force. Stiffness is the level of resistance maintaining its original shape. The carbon fiber materials used in making hydrogen fuel tanks is as light as a plastic but has six and four times the strength and stiffness of steel, respectively. “When a bullet penetrates a hydrogen tank, it does not explode. Instead, hydrogen leaks out through the bullet hole. In a standard collision test, not even a tiny amount of hydrogen was detected because none had leaked out. Compressed air production, storage and energy efficiency and density Compressed air has a low energy density, however near isothermal compressed air storage ICAES has almost 4 times lithium-ion batteries capacity with 2.7Mj/kg or 3.6Mj/m3. Compressed air can be produced by