The dream: Walk into the garage, hop in the back seat and say "take me to work."

The reality: Driverless cars exist -- Google (GOOG) and others are extensively testing them -- but they probably won't be chauffeuring you around anytime soon.

There's a mountain of red tape when it comes to permitting new auto technology, and people still aren't comfortable giving a machine full control of an automobile.

What's more likely is that this technology will continue showing up in bits and pieces -- cars that park themselves, smart cruise control that can slow down and speed up on the highway -- but retain an actual person in the driver's seat, at least for now.

When and if truly self driving cars arrive -- cars without a steering wheel, brake pedal or accelerator -- they'll likely start out in denser urban areas where they can be dispatched more like a taxi, said Lawrence Burns, a University of Michigan engineering professor and former head of R&D at General Motors.