Whenever we hear the latest buzz about driverless vehicles — like the ones currently in development by Google — one of the first benefits brought up is safety. The gist is that the vast majority of car accidents are the result of human error, and taking the human out of the equation would thus make streets a lot safer.

But that’s hardly the only benefit, suggests a new study in Nature Climate Change by Jeffrey Greenblatt and Samveg Saxena of the Lawrence Berkeley National Laboratory. The researchers model a future in which electric-powered driverless cabs or “autonomous taxis” roam the streets, in a range of sizes and specifically tasked to pick up a matching number of passengers for a given ride.

“[Autonomous taxis] are anticipated to be deployed according to each trip’s occupancy need (‘right-sizing’) because it is cost-effective for owners (capital and operating costs are lower) and passengers (who pay only for needed seats and storage),” the authors write. Smaller vehicles will save energy, and moreover, the authors project, there will be additional efficiency gains from two sources. These vehicles will be more likely to be electric, and thus powered from an increasingly renewable energy source; and they will travel considerably more miles per year,  meaning that more miles will be clean-powered.

It all adds up to a strong business case, meaning the vehicles would be “likely to gain rapid early market share.” The result is that by the year 2030, autonomous taxis could be dramatically cleaner not only than current cars, but also than projected hybrids in that year. The emissions reduction over cars we currently drive would be 87 to 94 percent, Greenblatt and Saxena find, and over future hybrids would be 63 to 82 percent.

The new study is “an exciting addition to the emerging field of analysis exploring the role of advanced connected and automated vehicles,” writes Austin Brown, a researcher with the National Renewable Energy Laboratory, in an accompanying commentary on the study.

This is not the only such study of late. Recent research by the OECD’s International Transport Forum has similarly found that there is vast potential for automated taxis to command a large market share in major cities. The study imagined “TaxiBots” and “AutoVots” that provided, respectively, shared rides for multiple passengers and services for single passengers. The upshot was similarly radical: Between 9 out of 10 current cars could be removed from the road, the research found, if these automated vehicles were combined with “high-capacity public transit.”

The OECD research also found environmental benefits — and for similar reasons. “TaxiBots and AutoVots are in use 12 hours and travel nearly 200 kilometres per day, compared to 50 minutes and 30 kilometers for privately-owned cars today,” noted the study. “More intense use means shorter vehicle lifecycles and thus quicker adoption of new, cleaner technologies across the car fleet.”

To be sure, such developments could add to the challenges faced by the taxi industry, which is already contending with competition from services like Uber and Lyft. “If [conventional] taxis vanish, the social impacts may be considerable,” note Greenblatt and Saxena.

“Shared self-driving car fleets will directly compete with urban taxi and public transport services, as currently organised. Such fleets might effectively become a new form of low capacity, high quality public transport. This is likely to cause significant labour issues,” adds the OECD study.

Other potential problems arise because humans may not choose to use robotaxis in the most energy-efficient manner, notes Brown of the National Renewable Energy Laboratory in his commentary. People might not choose the most efficient ride, he writes, especially if that is different from the fastest or more direct one. “The future of transportation energy consumption depends on how the system is used by people, and there are reasons to be cautious,” he notes.

Indeed, other research has recently suggested that driverless vehicles more generally could lead to an expansion of surburbia — an unwanted side-effect of a very new and powerful technology interacting with its human users. “When we are able to eat, sleep and work in our driverless cars, [travel time] will become longer, creating a burst of urban sprawl with its associated increases in energy consumption and adverse impacts on the land,” wrote two transportation researchers in Nature last week.

So in sum – driverless cars appear to be on the way, and it’s hard to imagine how they could be anything but disruptive. But just how much energy gets saved along the way remains to be determined.

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