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Is Ridesharing the Key to AV Success? We Talk to an Expert

April 10, 2019

The environmental impact of autonomous vehicles (AVs) is up in the air, but Judi Greenwald sees advantages to integrating them into fleets that provide mobility as a service.

We sat down with Greenwald, who will be moderating the policy panel at our upcoming Forum on Connected and Automated Vehicles: Energy Impacts, to discuss her new article in Energy Policy and why the future of AVs might be brighter if you can find them on a transportation app—not in your driveway. A former US Department of Energy official, she now runs Greenwald Consulting and is a visiting fellow at Princeton University’s Andlinger Center on Energy and the Environment.   


Here are excerpts from our conversation:

What’s driving the development of vehicle automation?

There are two big motivations—to increase mobility access and to make our roads safer.

We have a lot of car accidents in the United States and in the world. Even though we think we’re good drivers, we’re really not. Humans make mistakes. AVs have the potential to be safer than a conventional vehicle with a human driver, but whether we can operationalize this in the real world to achieve that promise is a question.

The other motivation is mobility. There are a lot of people who don’t have access to mobility. There are also a lot of people who can’t drive, like the old, the young, and the disabled. Many of these people live far from jobs and grocery stores and doctors and things they need to get to. And so there’s potential for AVs. While AVs will probably be expensive, if we have AVs as part of fleets that provide mobility as a service then they can really increase mobility access.

What will determine the environmental impact of AVs?

On the per-vehicle emission side, the most important things are the fuel economy standards. The fuel economy standards have been our biggest public policy success in controlling fuel use and greenhouse gas emissions, and people like them; they poll 70 plus percent [approval]. What we really should be doing is strengthening them, and making them work a little better for consumers and manufacturers.

The second most important thing is zero-emission vehicle (ZEV) mandates. Requiring every vehicle to have zero emissions now would be too expensive, but having a small percentage required to be super clean drives innovation for that sector.

On the vehicle miles traveled side, the biggest thing is ride sharing. If we have AVs that are just carrying one passenger (kind of like what we have now, where most personal vehicles carry one person the majority of the time), and if you have more people being driven by AVs than can currently drive themselves, then you’d have huge increase in vehicle miles traveled.

But if people rideshare, if you have autonomous vehicles taking two people to a place where they would have driven in their own cars, then you could be okay or potentially even better off. When I was at the Department of Energy, we calculated that there could be anywhere from a 60 percent reduction in fuel use for cars and light trucks to a 200 percent increase, or triple the fuel use.

Who owns these vehicles really matters. If AVs are owned by individuals, there is likely to be more of a vehicle miles travelled increase than if they are fleet owned by a company that provides mobility as a service.

Fleet owners are also better about doing the economic calculations for the vehicle itself. A fleet operator is going to be very sensitive to fuel costs, and it is going to want more efficiency. This means [fleets] will buy more efficient vehicles, and they’ll buy more electric vehicles. Because they use their vehicles more, they’ll get a quicker payoff from fuel savings, offsetting the higher upfront costs of the vehicles themselves.

When you or I own a car, that car spends 95% of its time parked. During the 5% of the time it is in motion, it’s usually just one person in the car. But if I’m a vehicle fleet owner, I’m going to use that vehicle way more, and I’m going to fill it up much more often. This motivates me to pay more up front for fuel efficiency because I’ll make my fuel savings back more quickly. 

The Forum will bring together people with a wide range of perspectives. What’s an AV-related challenge that calls for a better understanding between technology and policy experts?

Alain Kornhauser and I wrote the [Energy Policy] article together to try and get our two respective worlds to talk to each other more. Alain Kornhauser has been involved in autonomous vehicles for decades; he’s the head of the transportation program at Princeton University engineering school. He focuses on the safety and mobility of AVs. I’m focused on energy and environmental policy.

 In the safety and mobility transportation world, everyone is deep into autonomous vehicles, but in my world, on energy and environmental policy, people are paying very little attention to AVs. I worked on the US midcentury strategy for deep decarbonization for the Obama administration, and we didn’t even consider the implication of autonomous vehicles.

Our goal is to make sure that energy and environmental policy makers understand that the impact of AVs could go either way. It could either be a really good thing or a really bad thing, and we’d better pay attention and do something about it. And hopefully it will also cause people in Alain‘s world, the transportation and safety folks, to think about the energy and environmental implications of what they’re doing.  The key message that we have for the energy and environmental policy makers is that it’s up to us, and that’s actually the name of our paper: It’s up to us: Policies to improve climate outcomes from automated vehicles.”


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