Self-Driving Cars, Again

Published at 10:54 on 23 July 2016

I’ve become involved in a discussion about self-driving cars on an Internet forum, and the expected techno-utopian who thinks they will be a sea change which obsoletes mass transit has popped up. To summarize a past post, no, they won’t:

  • They will increase the capacity of existing freeways, but that’s nothing that building or expanding freeways doesn’t currently do, and such increased capacity falls victim to the induced demand problem. There is absolutely no reason to expect that the extra capacity furnished by self-driving cars will magically function differently than that furnished by more traditional means.
  • It’s actually worse than the above. By automating driving, self-driving cars will make driving easier. When you make something easier, the natural expectation is that people will do more of it. In other words, self-driving cars will themselves be a significant new inducer of demand for road space.
  • Some of the worst congestion is found on surface streets in commercial areas, where there isn’t much (or any) room for more cars on the existing streets. Self-driving cars will do nothing to alter this fact; automation does not repeal the basic laws of geometry. Quite the contrary; by increasing the capacity of freeways to deliver vehicles to such areas, they will exacerbate this congestion.

In fact, there’s a good chance that self-driving technology will make mass transit more relevant:

  • As demonstrated above, it will make congestion tend to get worse, thus increasing the need for alternatives to personal vehicles.
  • One of the largest costs for transit agencies (in fact, it’s typically the largest cost) is the labor cost for operating the transit vehicles. Self-driving buses will therefore enable significant savings for such agencies.
  • Labor costs are a big part of the reason why only big buses and not minibuses are used (the latter save very little money for agencies, because labor costs and not equipment or fuel costs dominate). By enabling minibuses to economically replace larger ones, self-driving buses will enable better, more frequent service to low-density areas that are difficult to serve well with traditional mass transit.
  • Self-driving cars will further help the ability of transit to serve low-density suburbia by making it easy for riders to get to train stations without requiring huge, expensive park-and-ride garages (which tend to fill up early). Riders can send the car back home after it drops them off; this won’t exacerbate congestion because travel will happen in the opposite direction, and residential streets (unlike freeways and commercial streets) typically don’t suffer congestion issues anyhow.

On top of all that, there’s energy efficiency and the need to reduce fossil fuel use. Self-driving cars still require several tons of steel to often carry just a single person around. The general wastefulness of the personal automobile remains unchanged.

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