Abstract: In a wheeled vehicle engine system comprising a compressed air powered engine and tank assemblies, an engine connects to the vehicle drive wheels and is powered by compressed air and operates without emitting air pollutants and the tank assembly comprises a replaceable and/or rechargeable main air tank assembly containing air at high pressure and recovery tanks both so connected to the engine and arranged so as to recover and store energy of the vehicle and engine developed during braking and high speed engine operation and not fully used to propel the vehicle. Pressure sensors and alternative valving arrangements of the tank assemblies actuate compressors driven by the motor to maximize utilization of the energy content of the tank assemblies.