Autonomous taxis could be cheaper and improve the environment, says Berkeley Lab study

July 6, 2015

Self-driving taxi? (credit: Google)

It’s the year 2030. A fleet of driverless taxis roams throughout your city, ready to pick you up and take you to your destination at a moment’s notice. As a result, greenhouse gases are now 63 to 82 percent lower than with a privately owned hybrid car and 90 percent lower than a 2014 gasoline-powered private vehicle. …

Those numbers are from a new study from Lawrence Berkeley National Laboratory (Berkeley Lab) published online today (July 6) by Nature Climate Change in an article titled, “Autonomous taxis could greatly reduce greenhouse gas emissions of U.S. light-duty vehicles.” Co-authored by Berkeley Lab scientists Jeffery Greenblatt and Samveg Saxena, it was funded in part by the Laboratory Directed Research and Development (LDRD) program at Berkeley Lab.

Almost half of those savings would be from “right-sizing,” where the size of the taxi deployed is tailored to each trip’s occupancy needs (assuming a fleet of taxis managed by a single entity). They suggest this illustration: consider a single passenger with no luggage versus a party of four passengers with suitcases. The single passenger would require a much smaller taxi than the party of four, saving money for vehicle owners and passengers (and the cost and extra energy required for a driver).

Self-driving cars have additional efficiencies that have been covered in other research, such as the ability to drive closely behind other autonomous cars to reduce wind resistance (“platooning”), optimally routing trips, and smoother acceleration and braking. “These are all incremental, but they do add up,” Greenblatt said. “However, we didn’t even include these effects in our baseline results, and we still get huge savings without them.”

Cost analysis: self-driving taxis cheaper

The researchers also conducted an economic analysis to determine how cost-effective autonomous taxis would be. At 12,000 miles per year, the average distance traveled in the U.S. for privately owned cars, electric vehicles in 2030 are still expected to be more expensive than owning and operating a gasoline-powered car, the study found.

But if the vehicle is driven 40,000 to 70,000 miles per year, typical for U.S. taxis, they found that an alternative-fuel vehicle (hydrogen fuel cell or electric battery) was the most cost-effective option. This was based on costs for maintenance, fuel, insurance, and the actual cost of the vehicle (assuming a five-year loan). The reason is that despite the higher cost of a more efficient vehicle, the per-mile cost of fuel is lower, so the savings can pay for the extra investment.

While autonomous technology is currently estimated to add as much as $150,000 to the cost of a vehicle, an autonomous taxi using today’s technology would still be cheaper than an ordinary taxi not simply due to its greater energy efficiency, but also due to the fact that no operator would be required. By 2030, autonomous taxis could be far cheaper than their driven counterparts.

The scientists did not try to estimate how widespread this technology would be in 2030. However, they did calculate that if five percent of 2030 vehicle sales (about 800,000 vehicles) were shifted to autonomous taxis, it would save about 7 million barrels of oil per year and reduce annual greenhouse gas emissions by between 2.1 and 2.4 million metric tons of CO2 per year, equal to the emissions savings from more than 1,000 two-megawatt wind turbines.

Furthermore, the scientists explored the net energy effect of combining ride-sharing with right-sized autonomous taxis. For example, if 10 percent of one-person rides were shifted to two-person rides, the total miles traveled would decrease 3.1 percent while average energy consumption (due to the larger vehicle) would increase 0.6 percent, resulting in a net energy decrease of 2.5 percent.

Why wait to 2030?

Meanwhile, Princeton’s Alain Kornhauser has a near-term, possibly more practical idea: a shared autonomous vehicle fleet could serve travelers needs with only half the number of cars on the road today, according to ExtremeTech. “He envisions a fleet of autonomous vehicles that will combine the convenience of not having to drive yourself with the flexibility of a scaled-up and always available Uber-like taxi service — and without the cost of hired drivers. His study [also] estimated that … parking needs and vehicle congestion would be greatly reduced.”

While laws are still uncertain, autonomous vehicles may soon be available. Google’s fleet of 20+ self-driving vehicles (with safety drivers) have self-driven nearly a million miles and is now averaging around 10,000 self-driven miles a week (a bit less than a typical American driver logs in a year), mostly on city streets, and never caused an accident, according to Chris Urmson, director of Google’s self-driving car program. “We’ve been involved in 11 minor accidents (light damage, no injuries) … and not once was the self-driving car the cause of the accident,” he said.

Meanwhile, Elon Musk has said he would introduce an automated steering feature for “major roads” like highways with a software update (not for use in cities or suburban areas). But a fully self-driving Cadillac CTS Sedan will hit the roads in 2017. And Volvo plans to put 100 self-driving XC90 crossovers on Swedish streets by 2017. The vehicles will be driven by ordinary people in Gothenburg using a controlled 31-mile route.

Google | Google Self-Driving Car on City Streets

Abstract of Autonomous taxis could greatly reduce greenhouse-gas emissions of US light-duty vehicles

Autonomous vehicles (AVs) are conveyances to move passengers or freight without human intervention. AVs are potentially disruptive both technologically and socially, with claimed benefits including increased safety, road utilization, driver productivity and energy savings. Here we estimate 2014 and 2030 greenhouse-gas (GHG) emissions and costs of autonomous taxis (ATs), a class of fully autonomous shared AVs likely to gain rapid early market share, through three synergistic effects: (1) future decreases in electricity GHG emissions intensity, (2) smaller vehicle sizes resulting from trip-specific AT deployment, and (3) higher annual vehicle-miles travelled (VMT), increasing high-efficiency (especially battery-electric) vehicle cost-effectiveness. Combined, these factors could result in decreased US per-mile GHG emissions in 2030 per AT deployed of 87–94% below current conventionally driven vehicles (CDVs), and 63–82% below projected 2030 hybrid vehicles, without including other energy-saving benefits of AVs. With these substantial GHG savings, ATs could enable GHG reductions even if total VMT, average speed and vehicle size increased substantially. Oil consumption would also be reduced by nearly 100%.