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Said Tara Grescoe: “The more I read about self-driving cars, the more I realize that nobody knows what they’ll mean for our cities.”

More evidence (something else that never occurred to me) from CityLab: 

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How Driverless Cars Could Make Traffic Dramatically Worse

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A new simulation-based study of driverless cars questions how well these two big secondary benefits—less traffic and more comfort—can coexist. Trains are conducive to productivity in large part because they aren’t as jerky as cars. But if driverless cars mimic the acceleration and deceleration of trains, speeding up and slowing down more smoothly for the rider’s sake, they might sacrifice much of their ability to relieve traffic in the process. …

… if we want riding in a driverless car to be as comfortable as riding in a train, we need to consider the possibility that more traffic will be the result. Le Vine and company conclude:

Our findings suggest a tension in the short run between these two anticipated benefits (more productive use of travel time and increased network capacity), at least in certain circumstances. It was found that the trade-off between capacity and passenger-comfort is greater if autonomous car occupants program their vehicles to keep within the constraints of HSR (in comparison to LRT).

DriverlessThe work is a reminder that the full benefits of a driverless-car world might take quite some time to materialize—and that we should prepare for the challenges, too. Le Vine acknowledges that congestion might very well clear up once every vehicle in the fleet is autonomous, or even once there are enough to create driverless platoons. Until then, however, the traffic outcomes are much less predictable and very possibly negative.

Consider, for instance, that these simulations didn’t include pedestrians. Doing so no doubt would have led to even more starting and stopping, and thus more delay. And if seatbelts remain mandatory in driverless cars, that might require smoother acceleration and deceleration; much of the comfort of a train ride, after all, is the lack of seat restraints. Traffic behavior would also change if manufacturers offer people several driving profile options—say, from ultra-smooth to aggressive.

All the more reason to think driverless cars will complement, rather than immediately replace, public transportation in cities.