COVID-19 Put the Brakes on Traffic and Emissions, But Will it Make a Difference?

A man and woman wearing masks and looking at their phones wait to board an approaching train
(Getty Images)

Shelter-in-place orders related to COVID-19 have nearly eliminated gridlock on California’s roadways. With fewer vehicles in use, carbon-dioxide emissions are down significantly. By some accounts, global daily emissions dropped by 17 percent in early April. But will the pandemic have any lasting impacts on how we use transportation and plan for the future?

To learn more, we spoke with Daniel Sperling, director of the Institute of Transportation Studies at UC Davis and distinguished professor in the Departments of Environmental Science and Policy, and Civil and Environmental Engineering.

Professor Daniel Sperling, director of the Institute of Transportation Studies at UC Davis. (Gregory Urquiaga/UC Davis)

What kind of transportation impacts are you seeing from the COVID-19 pandemic?

Stay-at-home orders have impacted all modes of transportation. It has been disastrous for airlines, ridesharing companies such as Lyft and Uber, transit operators, and shared bike and scooter services. There is also collateral damage to many related companies, such as car rentals, with Hertz filing for bankruptcy.

Transit was already in big trouble in the United States, with ridership waning for many years. Now, it’s a nightmare, with ridership drop-offs of over 90%. Vehicle use was down about 60 percent at the height of stay-at-home orders, but it is now heading back up.

All this adds up to a fairly significant drop in greenhouse gas emissions, not just for transportation but for the entire economy.

How might these trends inform future transportation policies and decisions?

With funding from our National Center on Sustainable Transportation, the State of California and others, we have been conducting a wide variety of research projects to understand changes in travel behavior and determine which behaviors are likely to persist and which are likely to revert back to the old normal. For instance, Giovanni Circella has been heading a series of surveys, begun before the pandemic, to track and explain changes over time. Early results of pandemic-induced changes will be out in July. Once we better understand and quantify the data, we will use it to inform policies.

Do you foresee any lasting impacts with regard to transportation-related emissions?

There are still many unknowns. The silver lining of the pandemic is that the air is much cleaner. In Los Angeles, Delhi and other big cities, the difference is really stunning. The big question is: Will people embrace this clean environment and clean air – and will it inspire them to behave differently at the ballot box and in their personal lives? Will they be more likely to buy an electric car and to vote for environmental policies that will keep the air clean?

As China has started opening up following COVID-19 lockdowns, we’re seeing a huge upsurge in personal vehicle use in major cities and a much slower re-embrace of public transit. There’s a fear of sharing space. As a result, emissions have not only resumed, but they may increase beyond pre-pandemic levels.

The implications of the pandemic – and its impacts on transportation – cut through the entire economy and society. We don’t yet know if businesses will shrink their office spaces or if telecommuting will become the norm. Will there be less business travel and long-distance travel? Will telemedicine and online meetings become the new normal? All of these things have the potential to reduce vehicle use and emissions, but that may depend on whether the pandemic persists and for how long.

Past research tells us that people’s behavior will likely revert back to what it was, but that may take two to three years. I think we’ll see a small increase in telecommuting over time, but the future of everything else is highly uncertain – including plane and transit travel.

How do these transportation trends relate to California’s climate goals?

Many of the gases we put into the atmosphere remain there for a hundred years or more. So, anything we do to curb emissions is a good thing.

More importantly, in terms of achieving deep, long-lasting cuts, California is leading the nation in adopting effective, forward-thinking policies. And doing it in a way that increases accessibility for the disadvantaged and assures that inequities of the past are lessened and even banished. State law requires a 40% reduction in greenhouse gas emissions by 2030 and an executive order calls for net-zero emissions by 2045.

If we’re going to achieve cuts of this magnitude in transportation, in a way that’s both equitable and good for the environment, we need to focus on two priorities: electrification and sharing.

The top priority by far is transforming almost all our cars, trucks and buses to electric propulsion, mostly using batteries, but also hydrogen. With the rapid decline in battery costs, it is not unreasonable that almost all cars and buses, and most trucks sold in California would be electric by 2035. Our Plug-In and Electric Vehicle Center at ITS, headed by Gil Tal, is playing a central role in formulating strategies and policies for California, the U.S. and China.

Another important goal is to restrain or reduce growth in vehicle use in a way that is equitable and accessible to all segments of the population. Sharing is key. Encouraging the use of public transportation, carpooling, ridesharing and micro-mobility options such as scooters and bikes all help.

woman rides JUMP bike through arboretum

A woman rides a JUMP bike through the UC Davis Arboretum. (Gregory Urquiaga/UC Davis)

You are helping California figure out how to achieve its goal of net-zero carbon emissions by 2045. Can you expand on that?

With Austin Brown, director of our Policy Institute for Energy, Environment, and the Economy, I’m helping lead a study funded by the California Legislature to recommend strategies and policies to get transportation to zero net carbon by 2045. Three other UC campuses are partners and the study is being closely monitored by all the key state agencies, who plan to widely promote the policy recommendations. At the same time, the United Nations’ Sustainable Development Solutions Network asked me and Lew Fulton of ITS, along with Austin and a few others, to lead a similar study for the U.S. Draft reports for both studies are due in September. In these reports, we will synthesize all the research conducted at UC Davis and elsewhere to provide policy and strategy recommendations to our nation.

In both studies, we will highlight policies that support and accelerate “good” trends that have emerged during the pandemic, those such as telecommuting that reduce emissions, and mitigate the “bad” trends, such as a reluctance to use public and shared transportation.

When it comes to making transportation decisions, what do you want the public to know?

Buy an electric car. Fly less often. Ride a bike for short trips. As restrictions begin to ease, look closely at the safety precautions for transit and ride-sharing. When it starts to feel safe, embrace sharing—and shed one of your cars. Finally, become informed and support transportation policies and initiatives at the local and state level that support electrification and sharing.

My overarching thought is that the pandemic and its associated lockdowns have provided a visible glimpse into how our collective decisions and behaviors impact air quality, carbon emissions and ultimately, the health of our planet. Hopefully, it inspires us to embrace new ways of traveling, eating, working and playing.


Dan Sperling would like to dedicate this interview to the memory of Tom Turrentine, founding director of the Plug-In Hybrid and Electric Vehicle Center at ITS-Davis, who passed away on June 2.

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