July 7, 2015

Self-driving taxis could help commuters and climate

by Julia Rosen

Today, if you need to get somewhere, you might catch a lift with another driver using a ride-sharing service like Uber. But twenty years from now, you might just catch a ride with a car — a driverless car. A handful of companies, like Google, Tesla, and Audi, are developing autonomous automobiles, and starting this year, you might even share the roads with their prototypes.

Of course, driverless cars aren’t really driverless; a computer loaded with maps and linked up to various sensors tells the car when to accelerate and how to steer (don’t worry, there’s also a human inside, ready to take the wheel when necessary). If this sounds like science fiction, consider the fact that many commercial cars already include some autonomous features, like the ability to park themselves and help drivers stay in their lane.

Leading the charge toward a driverless future, Google has championed the technology as a way to improve automobile safety. After all, more than 90% of U.S. car accidents result from driver error. Automated vehicles may also do a better job of spotting bikers and pedestrians. And advocates say that driverless cars could dramatically reduce congestion by communicating with vehicles around them and driving more efficiently.

Self-driving cars use sensors to determine the flow of traffic and avoid obstacles. (Credit: Sam Churchill via Flickr, CC BY 2.0)

Such changes in driving patterns could eliminate traffic jams and ease painful commutes, but they could also have big environmental benefits. That’s because self-driving cars could help lower the amount of planet-warming greenhouse gases emitted by automobiles. To start with, shorter following distances between cars would decrease drag, bringing down highway fuel consumption by as much as 20%, according to a recent report. And smart cars hooked up to the internet could find open parking spots without circling for hours — a task that currently consumes up to 40% of the fuel used in dense urban settings.

Now, a new study in the journal Nature Climate Change suggests that some of the first environmental benefits of self-driving cars may come from autonomous taxis. That’s because ferrying people around cities is just the kind of situation where the payoffs of driverless cars would likely outweigh the high cost of purchasing them, say the authors, Jeffery Greenblatt and Samveg Saxena of Lawrence Berkeley National Laboratory in California.

First of all, many of these autonomous taxis would probably be electric vehicles, which are cheaper to operate than conventional combustion engine cars or even hybrids. Battery-powered cars still need electricity, and producing electricity usually produces greenhouse gases. But electricity will get cleaner as renewable power sources expand; the U.S. Environmental Protection Agency hopes to reduce the amount of greenhouse gases produced by generating electricity by 30% by 2030.

Taxis also drive more than regular cars — a lot more — making efficient electric vehicles an even better bet, financially speaking (the more you drive the car, the lower the per-mile cost). In addition, autonomous taxis don’t have to be one-size-fits-all. If traveling alone, you could call a single-seater. If going on vacation with the whole family, you could summon a robo-minivan. Or, you could share a ride with a stranger, further increasing the fuel efficiency of the trip.

Here’s a video by Nature that illustrates the potential benefits of autonomous taxis.

Taking all these factors into account, the scientists calculated that autonomous taxis would produce 87 to 94% less greenhouse gases than their conventional counterparts by 2030. Even if hybrids have replaced all internal combustion engines by then, self-driving taxis could still reduce emissions by 63 to 82%.

However, the comfort and convenience of self-driving cars could backfire, at least from a climate point of view. For example, people might choose to drive — or be driven around — more often than they do now, since they can do other things while they ride. Or they may prefer more spacious driverless cars over the ones that fit their minimum requirements. The authors say that even if these things happened, autonomous taxis would still offer an environmental benefit over conventional cars, just a smaller one.

But before driverless taxis flood the streets, society needs to grapple with some important questions. For instance, who can operate a self-driving car and who is liable if one gets into a crash? Will there be negative consequences for public transportation or related industries? And the biggest questions of all: when and how will self-driving cars earn the public’s trust?


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Written by

Julia Rosen is a freelance science writer and PhD student at Oregon State University. She received a Bachelor’s degree in Geological and Environmental Sciences from Stanford University before beginning her doctoral research on polar ice cores and climate change. In between, she did her “Master's” in backpacking around the world and skiing. Julia is a periodic contributor to Oregon State’s research magazine, Terra, and helps write blog content and develop learning modules for Visionlearning.

The views expressed above do not necessarily represent those of Visionlearning or our funding agencies.

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