By 2030, electric-powered, self-driving taxis could produce one-20th the greenhouse-gas emissions (per mile) of the average car on the road today, according to a new scientific analysis.
Depending on how widely automated taxis are deployed, the shift could make a noticeable dent in total greenhouse-gas emissions, since transportation accounts for 13 percent of emissions worldwide today.
Two researchers from Lawrence Berkeley National Laboratory in California, Jeffery Greenblatt and Samveg Saxena, made the calculations in a study published in the journal Nature Climate Change today, concluding that automated taxis could produce per-mile emissions that are between 87 and 94 percent lower than those associated with the average car today. The amount of reduction depends on the potential variation in greenhouse-gas emissions associated with electricity in 2030.
The researchers’ scenario does, however, depend on a certain important assumptions. They expect that self-driving taxis would most likely be electrified and that the cars would be redesigned to be much more compact and efficient, to account for the lack of a driver and the often low number of passengers on board.
Even so, the study offers another important new perspective on the likely impact that greater vehicle automation could swiftly bring. “By considering what happens when you’re sharing, these vehicles enable much bigger energy savings,” says Greenblatt. “I was surprised by how much cheaper a battery-powered electric car is to operate when you run it for 70,000 miles a year.”
In recent years, significant progress has been made toward commercializing the technology needed to let vehicles drive automatically in many situations (see “Why Google’s Self-Driving Bubble Cars Might Catch On” and “When Will We Have Self-Driving Cars?”). Over the next few years, some car makers, such as GM and Tesla, plan to introduce fully automated highway driving technology.
It may take many years for complete automation to come to ordinary cars, but taxis could perhaps be automated more rapidly. There would be advantages to automating coördinated fleets of vehicles, especially for often-traveled routes. This could significantly change the transportation industry and potentially upend an entire sector of employment. The new study suggests that the environmental impact could also be profound.
“I do think that they are in the right ballpark in terms of reductions,” says Ryan Chin, a research scientist at the MIT Media Lab who studies the potential impact of automated vehicles.
Uber is another example of how technology has the potential to upend the taxi industry. The car service recently invested millions in setting up an automated-driving research center in Pittsburgh, luring researchers away from the prestigious robotics department at Carnegie Mellon University.
Previous work has suggested that even partial automation could offer significant energy benefits. A study produced by the Intelligent Transportation Society of America in 2014, for instance, found that increased use of automation in vehicles could result in a 2 to 4 percent reduction in gas consumption each year over the next decade.
Predicting how such a major technological shift will play out is inherently tricky, however.
“The future of transportation energy depends on how the system is used by people, and there are reasons to be cautious,” writes Austin Brown, a scientist at the National Renewable Energy Lab in Washington, in an accompanying article published in the same issue of Nature Climate Change. “Small, efficient vehicles will have to compete for customers with larger, comfort- or productivity-focused vehicles.”
Greenblatt and Saxena say that there would be benefits even with a noticeable uptick in travel (resulting in five times more energy use than their model assumes), but Brown argues that the convenience of on-demand, autonomous chauffeurs could encourage people to make many more trips than they do today. “There is no reliable estimate of how much demand may increase by when driving no longer requires a driver’s attention,” he writes.
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