Megan McArdle is a Bloomberg View columnist. She wrote for the Daily Beast, Newsweek, the Atlantic and the Economist and founded the blog Asymmetrical Information. She is the author of "“The Up Side of Down: Why Failing Well Is the Key to Success.” Read more opinion SHARE THIS ARTICLE Share Tweet Post Email

Photographer: STR/AFP/Getty Images Photographer: STR/AFP/Getty Images

The home state of Google Inc., the pioneering company in driverless cars, has just taken steps to make life more difficult -- not just for Google, but for all of us who would like to see driverless cars hit the road as soon as possible.

The California Department of Motor Vehicles has proposed new rules for driverless cars that would prohibit cars without a steering wheel or a brake pedal -- or a human driver ready to take the wheel. Obviously, this would be an enormous setback for Google’s program, which is evolving toward smaller, lower-speed vehicles with none of these things. In my opinion, it would also be a setback for the evolution of driverless cars.

There are basically two ways to innovate toward a “Level Four” truly autonomous car. The first is the way that most automakers have chosen: You innovate system by system, starting with a car that can handle some tasks on its own (like cruise control), and eventually arriving at a car that can handle all of them. In between, the car will be doing a lot of the driving, but a human will be standing by, ready to take over if needed.

There’s a big problem with this approach, however: the lag between when the car realizes it can’t handle a problem, and when the human can grab the wheel. Unfortunately, when the car has gotten into trouble is probably the exact moment when a lag in reaction time is most problematic.

And that presumes an attentive driver ready to assume command. That’s not necessarily a very realistic assumption. Even a driver who is trying to pay attention is likely to lose focus as she cruises along mile after mile with nothing happening. And real-world drivers aren’t that conscientious. They are going to give in to the temptation to read e-mail, apply lipstick, or engage in other tasks that will divert their attention. They may be rooting around in the backseat for a CD when the car runs into trouble.

They’ll also have lost some skill, if they’re regularly driving mostly autonomous vehicles. If you’re not used to making driving decisions, you’re going to be slower to make them in an emergency, which is when you most need to think quickly. This, and attention fatigue, is a problem that airline safety experts worry a lot about, now that modern autopilot systems are so competent.

You can solve some of these problems with technology -- by, for example, stopping the car if the driver removes her hands from the wheel. But that creates a problem of its own: A car that you almost never have to drive, but which nonetheless forces you to sit and watch the road, is almost worse than a car with no autonomous functions. Safety-wise, it may be a big improvement. But from the driver’s perspective, it’s a huge bore, which may impede demand for these kinds of systems.

So Google is moving toward the other approach: Take the driver out of the loop entirely. You start at Level Four automation, but slow and safe and in a limited range. At the moment, Google’s driverless cars are essentially well-padded golf carts. That has some drawbacks, since you can’t go very far very fast. But it does let you completely route around the safety issues that are created by mostly autonomous systems. As the company works out the bugs on driverless cars, it can gradually scale them up in speed and size, and expand their range.

This approach seems to me to be the one most likely to deliver us fully autonomous vehicles. At the very least, we should want both of these kinds of systems running in parallel, to see which one pays off (and of course, there’s no reason that both approaches can’t deliver insights and techniques that help developers on the other track). Forcing Google to put wheels and brakes back into its cars means reintroducing the very problems of human error and folly that we’re trying to engineer away.

Google can try to find a state with a more progress-friendly DMV, of course. But the company has already done an immense amount of work mapping the area around Mountain View. Letting that work go to waste because the government of California just can’t get past the old way of doing things would be a shame.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

To contact the author of this story:

Megan McArdle at mmcardle3@bloomberg.net

To contact the editor responsible for this story:

James Gibney at jgibney5@bloomberg.net