Promising improved safety, better fuel-efficiency and freedom from the boredom of long drives, autonomy has been coming piecemeal to our cars for some time - and it has always had its critics. In 1994, on a UK motorway, Jaguar and Lucas Industries demonstrated the safety of adaptive cruise control and automatic lane keeping; both technologies are now commonplace on our roads. The media were not impressed, describing the idea of cars that drive themselves as "madness".The incremental nature of technological change is an important factor in transport policy, yet too often transport planning chases "revolutions" where brand new (or redeveloped old) technologies will be widely deployed and adopted. As nice as a revolution may sound, that's just not how change actually occurs.
Rather than one day having a brand new model of fully autonomous vehicles, it is most likely that parts of the driving experience will be computerized (for instance fully autonomous freeway driving, just as fully autonomous parking is now commonplace) before the entire experience will be computerized. By encouraging and supporting incremental advances the technological, political and legal issues will have a chance to develop together, and adoption of new and safer technologies will happen faster. Consider what is happening with electric cars as a similar type of issue with deployment of new technologies. Electric cars are just not very popular as few people are adopting the revolutionary powertrains. The Chevy Volt is on hiatus, and Chevy just announced that it will be on hiatus an additional week. George W. Bush's "Freedom Car" and Arnold Schwarzenegger's "Hydrogen Highway" were failures, as was the entire "hydrogen revolution" because the infrastructure and technology isn't there to support widespread adoption, and still aren't. Maybe someday in the future hydrogen will be a standard fuel, but now people tend to really like their hybrids (Toyota is setting sales records with it's Prius models) which are an incremental improvement to what people already use.
All of this is to say don't hold your breath that autonomous vehicle technologies will first appear in a fully, full-time autonomous car, but also don't expect that driverless cars will not become commonplace. Drivers are already ceding some driving to their cars, and over time they will cede more and more until the driver is simply a passenger. Then someday no one will remember that is was ever any different.
UPDATE: Chevy announced that the Volt will go back into production on the original schedule due to strong March sales. Let's hope the strong sales continue!
UPDATE, Part Duex: Adam Ozimek at Modeled Behavior offers an alternative path to autonomous cars where demand for driverless cars comes from particular groups such as the elderly or disabled. This seems more along the lines of incremental shifts in the demographics of demand rather than incremental shifts in technology, as I argued.