Washington, July 7: A fleet of driverless taxis roaming a city to pick up passengers may not only be cost-effective, it could also greatly reduce per-mile emissions of greenhouse gases, say scientists, including one of Indian-origin.
Researchers from Lawrence Berkeley National Laboratory (Berkeley Lab) found that the per-mile greenhouse gas emissions of an electric vehicle deployed as a self-driving, or autonomous, taxi in 2030 would be 63 to 82 per cent lower than a projected 2030 hybrid vehicle driven as a privately owned car and 90 per cent lower than a 2014 gasoline-powered private vehicle.
Almost half of the savings is attributable to "right-sizing," where the size of the taxi deployed is tailored to each trip's occupancy needs.
"When we first started looking at autonomous vehicles, we found that, of all the variables we could consider, the use of autonomous vehicles as part of a shared transit system seemed to be the biggest lever that pointed to lower energy use per mile," said Berkeley Lab scientist Jeffery Greenblatt.
Many automakers and other companies are working on autonomous cars. Right-sizing is cost-effective for both the fleet owner and for passengers, and small one- and two-seat vehicles are being explored by researchers and companies.
"Most trips in the US are taken singly, meaning one- or two-seat cars would satisfy most trips," Greenblatt said.
"That gives us a factor of two savings, since smaller vehicles means reduced energy use and greenhouse gas emissions," said Greenblatt who co-authored the study published in Nature Climate Change with Samveg Saxena.
Another factor contributing to lower emissions for autonomous taxis is a cleaner electric grid. By 2030 power plants are expected to be using more renewable energy and emitting less pollution, meaning the greenhouse gas intensity of electricity will be lower.
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 travelled in the US 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 US 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 USD 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, researchers said.