Charon, what do you think of inertial batteries?  A coil is used to spin up a flywheel suspended on magnetic bearings in a vacuum.  So it can stay spinning at 100s of thousands of RPMs, and that kind of rotational speed means it doesn't have to weigh that much to store a large amount of energy.  The same coil that gets the flywheel spinning during 'charging' is later used to draw off electricity, slowing the flywheel back down.  For vehicular use, two or more flywheels could be set up in tandem, counter rotating to cancel the gyroscopic effect.

In Bowling Green Ky. back in the 1940's they had electric street cars the electric line was over head and rod like thing went to the electric line.The street cars were like bus's, rubber tires and no rails.They could go left and right about 10 feet from center to pull up to the curb.

I still think of them as golf carts, too. The official designation has been changed according to Wikipedia, I think as part of a UN-led initiative to standardize labels. We'll leave feelings and discussions about the UN to a different area of the forum.

Any street-legal car is required to have an effective windshield defrost system. That happened in the '60s as part of a Federal act, which also standardized shift patterns for automatic transmissions be requiring a Neutral position betweeen forward and reverse positions. Street-legal vehicles also must have headlights, tail lights, stop (brake) lights, turn signals, horn, and so on. As a practical matter this means there must be an electrical system, normally incorporating a storage battery. Air powered vehicles will not be exempt from these requirements, so they are going to need a battery and some way to charge it.

Cars and trucks with liquid-cooled internal combustion engines have a convenient source of hot water (since the engine wastes about a third ot the fuel's energy into the coolant). This is a no-cost source of heat for heaters and defrosters. The only "extras" are ductwork, an extra radiator (known as the heater core), and one or more electric blowers. Electric cars do not have the free heat. Many years ago someone marked a City Car (I think), and the problem of cabin heat was solved with a propane heater. The current electric cars use electric heaters, powered by the propulsion batteries, with the penalty of reduced range. Air conditioning requires a compressor, conveniently powered by the engine. If no engine, then a motor must be used, and range again is reduced. Most cars have power-assisted brakes, the power for which comes from engine vacuum. Diesels don't have engine vacuum, so the brake boost is derived elsewhere and that technology can likely be used for electric or air cars. An air car could use air brakes, but there may be licensing issues (air brake endorsement).

Speaking of brakes, right shortly (either the 2012 or 2013 model year, I think) a new Federal requirement takes effect requiring electronic stability systems on all cars and light trucks.  There is no way I know to implement such systems without computers, which means electrical power for actuators and controllers. Compressed air might be used for the main propulsion motors, but electricity will be needed for a lot of other stuff.

I'm sure others can come up with other issues and/or solutions.