yes u may run a car with pneumatic air pressure to run the vehicle, you need bulky cylinders to store the pressure or aircomprasser with high cfm delivery rate and pressure will be required which will again make the vehicle havey. Heavy vehicles have difficult controls and the speed issues to get momentum etc.

This may work in theory but I'm not sure of the technical sense. You'll need much energy to compress the air and while driving the pressure will of course decrease constantly. The concept may be appropriate for short distances, locally emisson-free. Maybe even in-house driving in big halls or so...

It will be very difficult to get any kind of useful range out of a stand-alone comressed air motor. If you assume isothermal expansion from 300 bar down to 2 bar, which is extremely optimistic, you can get 15 MJ out of a 100 liter air tank. One kg of gasoline has 44 MJ.

I agree with Per Tunestal. Energy density of air even at 300 bar is far below those of conventional fuels. To run an IC engine we need more than 30 bar peak cylinder pressure, but with realistic storage capacity, distance covered will be minimal. Thus making it impractical for current engine technology. Unless the idea is built parallel with new engine architecture, extremely lightweight vehicle body and excellent aerodynamic.

Beside the energy or power density i consider the cost of fuel as one of the main problems. A compressors wastes %80 of energy inputs as heat of compression. If we are thinking about future and see electrical vehicles are on the road the rival is not IC engines. So we compress air using electricity the cost will be higher than the Elec. Vehicles. Batteries have a defined lifetime and so have the compressors.

I dont think CA engines are will be on road in near future.