Policymakers have long pointed to two straightforward paths for cutting carbon emissions: cleaning up the vehicle fleet itself, by making it more efficient (and electrified), and reducing the total number of vehicle miles traveled (VMT).

While the new-vehicle front is affecting serious progress—likely soon slowed by pending changes to federal fuel economy standards—we’re undoing much of that with this continued trend: Americans are driving more.

The latest U.S. Department of Transportation update released last week, which uses data on hand through June 10, 2019, finds that in terms of vehicle miles traveled, Americans drove 2.5 percent more in April 2019, versus April 2018. Even seasonally adjusted—taking into account some larger trends, and adjusting for things like where weekends fall—there’s a 2.0 percent increase.

Traffic was up in all regions of the U.S., with a peak 3.0-percent rise in the West, which includes everything including and west of Montana, Wyoming, Colorado, and New Mexico.

Traffic in Atlanta, Georgia during rush hour (via Wikimedia)

Cumulative travel so far for this year is up, too―at 1.0 percent, to a 2019 running total of 1,020.8 billion miles of travel.

A rise in VMT relates to greenhouse gas emissions and criteria pollutants. It’s also been linked to more highway deaths and various public health issues, as more people spend time in their vehicles.

Overall VMT has been climbing steadily in the U.S. over the past 25 years—with the one exception being a period from 2008 through 2012 (the recession and period immediately following), when miles traveled fell and then flattened for a few years.

Driving is trending higher especially on what the federal government calls Urban Highway environments. To our knowledge there isn’t an existing analysis of why this trend exists, although it could be an indication of people leaving mass transit for car-sharing or ride-hailing options. Or it could be part of a continued trend requiring those with lower-paying jobs in many U.S. big cities to commute from outlying suburbs because of a lack of affordable housing near urban cores.

Update: New York State blocks congestion charge

According to the EPA, the average carbon dioxide emissions from a passenger vehicle in today’s fleet (2017 data) is 404 grams per mile. Model year 2017 vehicles averaged 348 grams per mile across the fleet. Electric vehicles get cleaner each year due to the greening of the grid. According to the Union of Concerned Scientists, the average electric car in the U.S. emits just 129 grams of CO2 per mile.

EPA Administrator Andrew Wheeler has said that choosing an electric car is "not grounds for concerns for the EPA."

If there’s a bright spot, it’s that that market share of plug-in vehicles—including electric vehicles and plug-in hybrids, which hopefully don’t involve tailpipe pollution in urban driving—rose from 1.16 percent in 2017 to 2.08 percent in 2018 (citing InsideEVs data).

Admittedly, that added up to just 361,000 vehicles nationally. With about 272 million vehicles registered in the U.S. as of 2017, it’s going to take a long time for those vehicles to make up a majority of traffic. If more Americans go electric and think a little bit more about why they’re driving so much, however, those seemingly minor changes could go a long way.