From Horseless to Driverless

Self-driving cars
There has been a lot of talk about automated vehicles, or self-driving cars. In fact, some aspects of vehicle automation already exist. If you’ve seen cars that can squeeze into a parking space themselves or slam on the brakes when the car in front gets too close, you’re familiar with low-level automation.

A self-driving car. Source.

Change is in the air
There is a lot of speculation about how automated vehicles may change the way we get around. Whether automation of cars will benefit the environment is harder to predict than you might expect.

Some people think automation will pave the way for a future where we don’t own cars. Instead, we would increase use of services like Uber and Lyft, which would be cheaper without drivers. On the flip side, we may end up driving much more. If you can check email or watch shows on your commute, you might not be as concerned about living close to work. Whether we share cars or buy our own will make a big difference in how many total miles are driven.

Travel might be more efficient with automation as well. Automated vehicles might be able to drive closer together and draft like bicycles in the Tour de France. These new vehicles might be smaller and lighter than today’s cars or they could be heavier. If we share vehicles, we may be able to use smaller cars when we are by ourselves and only use larger cars when truly needed. However, if we add features to make the ride more comfortable, that will add weight. These changes in weight have a big impact on efficiency.

Oh, the possibilities
These are very different possible futures. Scientists use scenario analysis to evaluate a wide range of possibilities. This means that they run calculations multiple times, changing the assumptions to see how the calculation changes. You may do something similar. If you are saving up for a trip, you might calculate how much money you can put toward the trip this month. You think you might be able to save $100 this month, but if you go out to lunch too often you will only have $70 to save. You have a similar estimate for each month until your trip. This helps you plan for your future trip because you have high and low estimates for how much you will have saved before you leave. The researchers did similar calculations on a computer with a lot more numbers.

A representation of some possible future scenarios. Source: author created.

For this work, the researchers considered four possible scenarios of how automated vehicles might change our travel patterns. In one scenario, we ride in small cars that are programmed to reduce fuel use. In another scenario, we ride in similarly small, efficient vehicles, but we drive them more. In a third, there are legal challenges that limit automation so not much changes. In a fourth scenario, we travel much more and the fuel use per mile goes up. None of these scenarios are predictions of the future, but they help us think through what it might mean to have automated vehicles. This means we can start solving problems early instead of waiting until something bad happens. For instance, if emissions are likely to go up, policy-makers can put rules in place to stop it before air quality gets bad.

What will happen?
The carbon footprint of our automated cars will be determined in large part by energy consumption. Riding in a car, with or without a driver, uses energy. Energy is associated with CO2 emissions. The different scenarios have huge differences in fuel use. In the scenarios with small, efficient vehicles, a lot less fuel is needed. In the scenario where we travel much more, we will need a lot more energy to power our cars. Using less energy to power your car means less CO2 is emitted, which is good news for the climate. Transportation is now the largest source of greenhouse gas emissions in the US, so lowering those emissions is important.

Testing of a self-driving car. Source.

We are also concerned about how clean the air we breathe is. Dirty air can harm our heart and lungs. Currently, the emissions that affect our health are controlled (for example by your catalytic converter) to meet regulations. If vehicles become much more efficient, this might meet the emissions standards that are already in place, but the car makers will not have a reason to reduce emissions further. Therefore, using less energy will not necessarily make the air cleaner. If we care about air quality, how we power our cars matters. If we have very efficient cars that don’t need much fuel, there isn’t as much motivation to shift away from traditional gasoline vehicles. In the small, efficient car scenarios, we produce more emissions that can hurt our health from poor air quality. However, if we need a lot of energy for our cars, there’s more of an incentive to drive electric vehicles because they are energy efficient and electricity is not as expensive. Poor air quality can make us sick, but switching to cleaner fuels helps us clean up the air.

The Takeaway
Using less energy to get around releases less CO2 into the atmosphere. That is great! Sharing vehicles or riding in smaller vehicles will help us use less energy, and automated vehicles might make that easier. We can enjoy a future of invisible robot chauffeurs, but let’s hope they keep our air (and our heart and lungs) healthy, too.

This study provided useful information about how vehicle automation could affect our environment. You can take steps now to make sure transportation is good for the environment. Commuting with family members or coworkers and relying more on public transportation are ways that you can share vehicles to ride cleaner. You can also tell your representatives and city planners that clean and efficient transportation is a priority for you as a constituent.

Source article: 

Brown, K., Dodder, R., Energy and Emissions Implications of Automated Vehicles in the US Energy System. Transportation Research Part D: Transport and Environment. 77, p 132-147. DOI: 10.1016/j.trd.2019.09.003

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Kristen Brown

Kristen Brown

I am a postdoctoral researcher at the EPA where I specialize in evaluating environmental impacts of our energy system. I have a PhD in Environmental Engineering from CU Boulder where I also received a master’s in Mechanical Engineering, and I have a BA in Physics from Cal Berkeley. Outside of work, I’m an amateur boxer and have two spoiled dogs. You can follow me on twitter at @Kris10BrownPhD and find out about my research at

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