A new report from the Road Ecology Center at the University of California, Davis has found that total US vehicle miles traveled (VMT) at the county and state level have declined by 61% to 90% following the various government stay-at-home orders in response to the COVID-19 pandemic.

Using data from StreetLight, the researchers estimated changes in daily vehicle miles traveled across the US before and after government shelter-in-place guidance. The difference amounted to a drop from 103 billion miles in early March to 29 billion miles during the second week of April. All states reduced their vehicle miles traveled by at least 60%.

The authors used the VMT data to calculate that emissions of US greenhouse gas (GHG) emissions were reduced by 4% in total and by 13% from transportation in the almost 8 weeks since many stay-at-home orders went into effect. This puts the US on track to meet its annual goals for GHG reduction under the Paris Climate Accord.

California has a target of 80% reduction in GHG from 1990 levels by 2050. If traffic remained reduced for one year, the reduction in VMT would allow California to meet half of its 2050 climate change target.

Greenhouse gas emissions reductions from road transportation were down across the United States from early March to early April 2020. (UC Davis Road Ecology Center)

The reduction in VMT per state was correlated with the number of COVID-19 cases and number of deaths (per 100,000 population)—i.e.,the more COVID-19 cases and deaths a state had, the greater its reduction in traffic.

New York carried the highest rate of cases during the reporting period. Drivers there and in the surrounding states of New Jersey, New York, Rhode Island, Connecticut, Massachusetts and Vermont drove at least 80% fewer miles after shelter-in-place directives began. Nearby Washington DC saw the greatest drop of 90% fewer daily vehicle miles traveled.

State-level relationship between reduction in VMT (%) and the number of cases per 100,000 people.(UC Davis Road Ecology Center)

Fuel saved, tax revenue lost. Fuel use dropped from 4.6 billion gallons in early March to 1.3 billion gallons during the second week of April, saving US drivers $8.6 billion per week. It also resulted in fuel-tax revenue reductions, which vary by state.

In California, where vehicle miles dropped more than 75%, the state’s fuel-tax revenue under Senate Bill 1 (2017) also plummeted from $61 million in early March to $15 million for the second week of April. For an eight-week, stay-at-home order, the loss to the state is an estimated $370 million in funds that support highway construction, maintenance and transit improvements aimed at reducing emissions.

The study acknowledges that the emissions benefits of stay-at-home orders could go away once normal activity resumes.