The main disadvantage is their cost (due to the need for a compressor station and a distribution system). A pneumatic engine with a rectilinear motion is most commonly used in automatization. It is composed of the main body, a piston, and a piston rod. A pneumatic engine with an oscillating motion is, in principle, an engine with rotational motion; however, they have a limited angle of rotation. They are used in high-pressure pumps. Therefore, there are some fields in which pneumatic mechanisms, i.e., engines, can be used. Despite a few disadvantages, some researchers and scientists developed vehicles that are powered by pneumatic engines [20; 21; 22]. The application of a drive train powered by compressed air could be more ecological because such drive trains do not employ the combustion processes of fossil fuels. Compressed air-powered propulsion systems for transport means are developed, and they attract research focuses. Alternatively, compressed air engines can be integrated as a part of hybrid systems, including a conventional combustion engine. Such a hybrid powertrain system can be considered as a transition vehicles power system between the fossil-fueled combustion engine and zero-emission propulsion system, such as an electric power unit or a compressed air powered unit [17; 19; 23; 24]. This type of vehicle, called a pneumobil, could be used in places where the production of gas emissions is undesirable, e.g., in production halls, enclosed spaces, and town centers. Thus far, the use of compressed air engines was limited due to the insufficient supply of a medium [18]. The first pneumobil in the Czech Republic was designed at the Brno University of Technology in 2011 [25]. This vehicle is powered by compressed air stored in air reservoirs. The very first prototype ran a track with a length of 3 km at a speed of approximately 40 km/h. In 2018, this pneumobil was able to run a 7 km track at a speed of 50 km/h [26]. In Slovakia, researchers from the Technical University of Kosice introduced their first pneumobil in 2018 [27]. This vehicle is equipped with a three-cylinder engine powered by compressed air with a displacement of 1.9 l. The air reservoir has a volume of 10 L, and the maximal pressure of the compressed air is 20 MPa. Research on the application of compressed air engines is also being performed at other institutions. The majority of prototypes of the compressed air engines come from modifications of conventional internal combustion engines. For instance, researchers from Zhejiang University conducted studies with a modified single-cylinder diesel engine, and they created an engine from compressed air. Its maximal power reached the value of 2.6 kW at an air pressure of 0.8 MPa [19; 28]. The team from the National Tsing Hua University developed compressed air engines based on a conventional motorcycle engine. The experiments proved the maximal power of 0.96 kW at the air pressure of 0.9 MPa. A modified engine has had the maximal power of 2.15 kW under the air pressure of 1.3 MPa, and the motorcycle was able to drive at the speed of 38.2 km/h for 5 km [19; 21]. Although the pneumobil is currently used in the automotive industry's development and research competitions between universities [29; 30], it is still being developed and improved. The main goal is to develop an easily handled vehicle that would contribute to reducing environmental impacts and noise while driving as long a distance as possible [23]. Moreover, the automotive company PSA worked on the development of a car powered by compressed air that would replace the electromotors in the company's hybrid vehicles [31]. Tata Motors of India was another vehicle manufacturer that developed a vehicle powered by a pneumatic engine. The compressed air engine should be used in the modified model Nano, which was previously under consideration as part of their collaboration with the MDI vehicle manufacturer [19; 32]. There were also other lesser-known companies that have worked on the development of a compressed air engine.