Have you seen CMU's Palm Pilot Robot? If you haven't, check out the first link below.
A very cool thing about it is it's holonomic drive system. Being able to move holonomically means "it may move in any direction while simultaneously controlling rotational speed." (For a fuller explanation, see the second link.)
If we scale it up to a car, this means you'll be able to drive in any direction, rotate in place, or even rotate while moving down the road. No backing and filling into tight parking spots-- just slip sideways into it. Drive straight into your garage, then rotate in place so you can drive straight out again instead of backing out. "Turn radius" will be a thing of the past-- you can do a U-turn in any amount of space!
One downside is that I don't imagine holonomic wheels would be very good at highway speeds-- but I could be wrong. If that's the case, then holonomic cars could be city drivers (and as such, be electric) while you use your old non-holo car for long distance treks.
The controls will have to change as well-- the steering wheel could control rotation (in which case it would spin freely, instead of turning three times lock-to-lock), and a joystick could control direction. They would also be linked so that your car would automatically turn to face the direction you were travelling unless you overrode it, and vice-versa. Turn signals will be more complicated, but since so few people signal anyway it shouldn't be a problem.
Three wheels good, four wheels bad!-- ejs, May 22 2001 Palm Pilot Robot Overview http://www.cs.cmu.edu/~pprk/overview.html [ejs, May 22 2001, last modified Oct 04 2004] Description of Holonomic Movement http://www.cs.cmu.edu/~pprk/physics.html [ejs, May 22 2001, last modified Oct 04 2004] Dymaxion Car http://www.wnet.org/bucky/car.htmlAnother approach to solving these problems. [egnor, May 22 2001, last modified Oct 04 2004] (?) Omni-directional vehicle http://www.onr.navy...htransfer/taa25.htmUnfortunately, it seems that the US Navy is baking this superb idea. [angel, May 22 2001, last modified Oct 04 2004] (?) Omni-directional vehicle picture http://popularmecha...ech/9506TUMIKM.htmlInteresting take, but these wheels also look ill-suited for highway speeds. [ejs, May 22 2001, last modified Oct 04 2004] Moller Sky Car http://www.moller.com/Click on the pic. [AJCrowley, Oct 04 2004] Nissan Pivo 2 http://www.youtube....watch?v=MfYdas0OiTIHolonomic. And even the cabin can turn. [fungowski, Jul 13 2009] Couch Car http://www.youtube....watch?v=tlf01rk8hIQFrom "Prototype This!", Discovery Channel [fungowski, Jul 13 2009] Perhaps someone could develop holonomic hybrids that alter their configuration (perhaps with a dropdown fourth wheel) for higher speeds.-- centauri, May 22 2001 Hey, nice one! I just read a description of Jacques Costeau's first submersible "saucer," and it did this kind of thing except of course underwater.-- Dog Ed, May 22 2001 I'd like to sell my car, but keep the interior since what went on there is my business. I'm used to it by now. Please suggest that your cars be designed to allow the interchange of cabins. That will make getting a loaner while down for repairs soo much easier.-- reensure, May 22 2001 Soterios: Your modifications would make a perfect Mars rover.
Mephista: Good idea. Perhaps the engines powering the wheels would just engage special gears to turn the cabin, so you wouldn't need another engine just for the bubble.
Egnor: My longtime dream has been to start a company that built updated versions of the Dymaxion car. If there were a Dymaxion car on the market today, I would be driving it.-- ejs, May 23 2001 Stuff all cars and buy the Moller Sky Car. See link...-- AJCrowley, Apr 20 2003 I suppose you could have a "Holonomic" setting on your gear shift, although it'd be a shock if you accidentally tried to shift into "sideways" while barrelling down the highway and suddenly find your wheels have been ripped off.-- Abusementpark, Dec 10 2006 random, halfbakery