Unexpected downside to driverless cars shown
Study says robot vehicles could use up more fuel
Driverless cars had better be able to refuel themselves. They’ll consume more energy than cars with drivers.
That’s the somewhat counterintuitive conclusion in a new study by researchers at the University of Michigan in Ann Arbor. They say that autonomous autos could reverse a years-long trend of declining fuel consumption.
At least a half-dozen car and technology companies, from General Motors Co. to Google Inc., are developing the futuristic vehicles, which would be guided by sensors and satellite positioning. Baidu Inc., the Beijing-based searchengine company, said Monday it could have a model on the road this year.
Here’s how they’d use more energy than conventional cars: more trips. In most households, each adult commutes, runs errands and shuttles the kids separately, according to the U.S. National Household Travel Survey. A selfdriving car would make more trips to finish the same tasks, the University of Michigan researchers said. It might drop off one parent at work, return home to pick up the other, and then take the kids to school, return home, then start the return cycle.
What isn’t known yet is how many people who don’t currently drive, like kids and users of public transportation, will start sharing a self-driving car.
Those new trips — and all the return trips in between — could mean more total driving.
Increased sharing could mean Americans would own 43 per cent fewer cars (from 2.1 to 1.2 vehicles per household) but use them 75 per cent more (from 18,766 to 32,804 annual kilometres per vehicle), according to calculations by Brandon Schoettle and Michael Sivak of the University of Michigan Transportation Research Institute. Their funding comes from federal and state government agencies and auto manufacturers and suppliers.
“It could be that sharing the vehicle ends up increasing the mileage because of all these connecting trips,” Schoettle said. “The net effect is probably going to be an increase in mileage, and in general the more miles you drive the more fuel you burn.”
There’s a caveat. Automated cars might prove to be better at conserving fuel because they wouldn’t waste fuel flooring the accelerator and slamming on the brakes, like humans do, Schoettle said. They’d be better at avoiding traffic jams and red lights, and would find parking spots without driving around and around and around. Also, ridehailing apps like those offered by Uber Technologies Inc. and Lyft Inc. could make sharing more efficient.
“Shared autonomous vehicles” could use 12 per cent less fuel and release 5.6 per cent less climatewarming gas than average cars, according to a 2014 study by researchers at the University of Texas at Austin..
Five U.S. states have passed laws allowing robot cars, with certain conditions, and six more are considering them, according to researchers at Stanford Law School.