A new study published by the Lawrence Berkeley National Laboratory (Berkeley Lab) suggests that utilizing autonomous electrified vehicles as driverless taxis can maximize the technology’s potential.
The research team, which includes Berkeley Lab scientists Jeffery Greenblatt and Samveg Saxena, said lower carbon emissions, lower energy costs and cheaper maintenance were among the benefits of self-driving electrified vehicles (EVs).
“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 Greenblatt.
The study focuses on autonomous EVs in general, and the researchers don’t specify if the vehicle uses a battery electric, fuel cell or other type of electrified powertrain. Factors analyzed in the study include greenhouse gas emissions, vehicle size, average number of trips per person and cost per mile.
The Berkeley researchers aren’t the only ones who see the potential for self-driving taxis. Travis Kalanick, the CEO of ride service company Uber, recently remarked that in 2020 he would buy every one of Tesla’s autonomous cars to use as driverless taxis.
Last month, venture capitalist Steve Jurvetson also named self-driving taxis as one of the hottest upcoming tech trends, saying the technolgy combination blends time efficiency, fuel savings and safer transportation.
Lower Carbon Emissions
It’s not surprising that the study’s results show that autonomous taxis are more efficient than current gasoline vehicles. What is significant is the amount of carbon emissions that will be saved, even in comparison to the predicted output of a future hybrid vehicle.
“The analysis 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 percent lower than a projected 2030 hybrid vehicle driven as a privately owned car and 90 percent lower than a 2014 gasoline-powered private vehicle,” said Julie Chao with the Berkeley Lab.
Vehicle Size is Important
Sending out the right vehicle size to pick up passengers is a key factor to the carbon equation, said the researchers.
“Most trips in the U.S. 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.”
According to the study, tailoring the taxi to the size of the party – called “right-sizing” – results in almost half of the vehicle’s carbon emission savings. This approach, however, requires the taxi service to have a range of vehicle sizes to send out the best size each time. Ride sharing – shifting a one-person cab ride to a two-person ride – would further reduce energy consumption.
Both energy savings (the cost of recharging EV batteries in comparison to the cost of gasoline) and maintenance expenses were predicted to be less for the self-driving taxis.
“You don’t often find that, where the cheapest is also the greenest,” Greenblatt said.
The caveat is that savings are seen after 40,000 annual miles have been clocked on the odometer. At around 12,000 miles, the average distance for privately owned vehicles, EVs were more expensive to own.
“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,” said Chao. “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.”
Even after adding in the anticipated $150,000 to add the autonomous technology, the researchers calculate that an autonomous taxi will still be less expensive to own and operate than a traditional taxi.
Chao listed additional benefits to autonomous taxis, including “the ability to drive closely behind other autonomous cars to reduce wind resistance (‘platooning’), optimally routing trips, and smoother acceleration and braking.”
However, the researchers opted not to delve deeper into these particular elements for their study.
“These are all incremental [advantages], 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.”
For the study, the researchers also assumed that by 2030, the power plants responsible for generating electricity to charge the vehicles will also be cleaner, resulting in more greenhouse gas savings.
From here, Greenblatt wants to look deeper into battery degradation and vehicle designs to make a “more realistic simulation of how a fleet of autonomous taxis would actually operate in a metropolitan area.”
Greenblatt and Saxena’s full study, “Autonomous taxis could greatly reduce greenhouse gas emissions of U.S. light-duty vehicles,” was published by Nature Climate Change, and can be read online.