Will you need a licence to operate a self-driving car?

If you're stopped by police in your self-driving vehicle, would you need to show a driver's licence? This is not a riddle, it's a legitimate question to be debated by lawmakers when they begin to address the reality of a world where not all cars and trucks have humans at the wheel.

Yes, the driverless car is coming - much sooner than you think. Ford says that within five years it will have a fully self-driving vehicle without steering wheel, gas or brake pedal for sale to ride-hailing companies. Uber is ready now to pick up passengers in Pittsburgh with an experimental version of an autonomous vehicle that uses a human driver as backup. GM, Toyota, Tesla, Google, Nissan, VW and maybe Apple all are feverishly at work on the driverless car.

As much as the robot-mobile conjures images of a weird distant future, the technology is advancing so rapidly that it's time to go beyond the gee-whiz factor and contemplate the vast social, economic and legal changes this revolution will bring.

Think about how the smartphone changed your life. Think about what happened when the Model T replaced the horse. Now think about computer-driven transportation, with you in the back seat, snoozing, texting or getting some work done as your drone chauffeur merges onto the  freeway .

About 90 per cent of traffic crashes are caused at least in part by driver error. With computers in control, relying on sensors and GPS, driving becomes safer and more efficient. Cars, trucks and buses could zip along at higher speeds, in close proximity like a pack of Tour de France cyclists. That will have an impact on real estate values. Those living near cities could move to outlying areas because they don't fear the faster, less perilous rush-hour traffic. In the city, meanwhile, parking lots become less important, because commuters can send their vehicles to distant garages for the day. Maybe urban vehicle ownership fades away, replaced by Uber or Lyft memberships. Why hassle with street parking when ride-hailing cars, or communally owned vehicles, continually prowl the streets?

A more jarring repercussion will affect jobs. Millions of truck drivers, bus drivers, Uber drivers and others will be displaced by computers. They'll need to find new work, probably requiring more education, as technology replaces low-skill labor.

Bryant Walker Smith, a University of South Carolina law professor and noted thinker on self-driving cars, says that as tough as those losses will be, he sees potential benefits, too. People living in poor areas will find improved access to job opportunities because ride-sharing becomes cheap and easy enough to transport people to distant workplaces.

Amazing how quickly appreciation for an engineering marvel leads to deep questions about issues as varied as urban planning and the social safety net. Innovation, Smith says, is about replacing one set of problems with another and hoping that, in aggregate, the new set is smaller. For example: Come the driving revolution, what happens to the commuter rail system? Do trains become more important or less? Can this technology be kept safe from hackers and terrorists? And, how about the future of red light cameras as a revenue generator? You can bet the robots won't mindlessly blow through intersections.

There are also nitty-gritty issues for government to address. Vehicle safety regulations have to be updated, as do traffic laws. And what of that question about driver's licences? You don't need one to be a bus passenger, so you wouldn't need one to own a driverless car, right?

Here's another puzzle: If you're caught intoxicated in a self-driving vehicle, should you get arrested or praised? David Strickland, a spokesman for the driverless car industry, who also happens to be chairman of US organisation Mothers Against Drunk Driving, tells us he thinks DUI laws would disappear because they are intended to prevent people from becoming a danger behind the wheel. "If you have a car that drives itself, you don't have that problem anymore."