Short post here. I notice people are writing about self-driving cars a lot. There is a lot of excitement out there about our driverless future.
I have a few thoughts, to expand on at a later day:
Apparently a lot of economic work on driving suggests that the a major externality of driving is from congestion. Simply, your being on the road slows down other people’s trips and causes them to burn more gas. It’s an externality because it is a cost of driving that you cause but don’t pay.
Now, people are projecting that a future society of driverless cars will make driving cheaper by 1) eliminating drivers (duh) and 2) getting more utilization out of cars. That is, mostly, our cars sit in parking spaces, but in a driverless world, people might not own cars so much anymore, but rent them by the trip. Such cars would be much better utilized and, in theory, cheaper on a per-trip basis.
So, if I understand my micro econ at all, people will use cars more because they’ll be cheaper. All else equal, that should increase congestion, since in our model, congestion is an externality. Et voila, a bad outcome.
But, you say, driverless cars will operate more efficiently, and make more efficient use of the roadways, and so they generate less congestion than stupid, lazy, dangerous, unpredictable human drivers. This may be so, but I will caution with a couple of ideas. First, how much less congestion will a driverless trip cause than a user-operated one? 75% as much? Half? Is this enough to offset the effect mentioned above? Maybe.
But there is something else that concerns me: the difference between soft- and hard-limits.
Congestion as we experience it today, seems to come on gradually as traffic approaches certain limits. You’ve got cars on the freeway, you add cars, things get slower. Eventually, things somewhat suddenly get a lot slower, but even then it’s certain times of the day, in certain weather, etc.
Now enter a driverless cars that utilize capacity much more effectively. Huzzah! More cars on the road getting where they want, faster. What worries me is that was is really happening is not that the limits are raised, but that we are operating the system much close to existing, real limits. Furthermore, now that automation is sucking out all the marrow from the road bone — the limits become hard walls, not gradual at all.
So, imagine traffic is flowing smoothly until a malfunction causes an accident, or a tire blows out, or there is a foreign object in the road — and suddenly the driverless cars sense the problem, resulting in a full-scale insta-jam, perhaps of epic proportions, in theory, locking up an entire city nearly instantaneously. Everyone is safely stopped, but stuck.
And even scarier than that is the notion that the programmers did not anticipate such a problem, and the car software is not smart enough to untangle it. Human drivers, for example, might, in an unusual situation, use shoulders or make illegal u-turns in order to extricate themselves from a serious problem. That’d be unacceptable in a normal situation, but perhaps the right move in an abnormal one. Have you ever had a cop the scene of an accident wave at you to do something weird? I have.
Will self-driving cars be able to improvise? This is an AI problem well beyond that of “merely” driving.”
Speaking of capacity and efficiency, I’ll be very interested to see how we make trade-offs of these versus safety. I do not think technology will make these trade-offs go away at all. Moving faster, closer will still be more dangerous than going slowly far apart. And these are the essential ingredients in better road capacity utilization.
What will be different will be how and when such decisions are made. In humans, the decision is made implicitly by the driver moment by moment. It depends on training, disposition, weather, light, fatigue, even mood. You might start out a trip cautiously and drive more recklessly later, like when you’re trying to eat fast food in your car. The track record for humans is rather poor, so I suspect that driverless cars will do much better overall.
But someone will still have to decide what is the right balance of safety and efficiency, and it might be taken out of the hands of passengers. This could go different ways. In a liability-driven culture me way end up with a system that is safer but maybe less efficient than what we have now. (call it “little old lady mode”) or we could end up with decisions by others forcing us to take on more risk than we’d prefer if we want to use the road system.
I recently read in the June IEEE Spectrum (no link, print version only) that some people are suggesting that driverless cars will be a good justification for the dismantlement of public transit. Wow, that is a bad idea of epic proportions. If, in the first half of the 21st century, the world not only continues to embrace car culture, but doubles down to the exclusion of other means of mobility, I’m going to be ill.
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That was a bit more than I had intended to write. Anyway, one other thought is that driverless cars may be farther off than we thought. In a recent talk, Chris Urmson, the director of the Google car project explains that the driverless cars of our imaginations — the fully autonomous, all conditions, all mission cars — may be 30 years off or more. What will come sooner are a succession of technologies that will reduce driver workload.
So, I suspect we’ll have plenty of time to think about this. Moreover, the nearly 7% of our workforce that works in transportation will have some time to plan.