States must step up efforts to reduce harmful carbon emissions

By Chris McCahill and Megan Link 

As of last September, 16 states and Puerto Rico approved legislation requiring reductions in greenhouse emissions. The White House also set ambitious goals of cutting emissions by at least 50% below 2005 levels in 2030. They aim to achieve a net-zero economy by 2050. 

Contributing to 29% of all greenhouse gas emissions in the U.S., the transportation sector is now the top producer and accounts for a growing portion each year. More than half of these emissions (57%) come from personal vehicles such as cars, SUVs, and light-duty trucks. Progress in cutting those emissions has been slow, let alone efforts to measure and track them. 

The federal government recently implemented a rule requiring states to measure transportation emissions, set targets, and report progress regularly. But that modest step was soon halted by courts in two states. Some states continue to monitor emissions on their own, but there is still no consolidated source of information on where they stand. So, we crunched some numbers. 

Explore the dashboard

How are the states doing? 

The short answer: not great. But the story is different from state to state. We analyzed recent trends in vehicle electrification, clean energy, and overall vehicle use for a clearer picture of the coming decade. We packaged our findings in a convenient dashboard so you can explore the trends in different states and understand the factors at play. 

For example, we compared Minnesota and Wisconsin, two neighboring Midwestern states with considerably different trajectories. Emissions in Minnesota are on track to drop 8% below 2019 levels in 2035, while Wisconsin could see a 4% increase.

Each state has just under 6 million residents and a similar mixture of urban and rural places. Based on recent trends, Wisconsin’s population could grow by around 6% to 7% in 2035, while Minnesota could grow by around 10%. In many cases, this rate of growth presents a challenge for lowering emissions. But Minnesota has several key advantages. 

First, at the current rate, Minnesota could see emissions per kWh of electricity drop by two-thirds, which would effectively lower EV emissions by the same amount. Wisconsin is on track for a reduction closer to 40%. 

Second, Minnesota’s electric vehicle fleet could grow five-fold to 12%, whereas Wisconsin may be closer to 8%. This does not account for potential incentive programs or major shifts within the automotive industry.  

Combined, these amount to 10% fewer emissions per mile in Minnesota and 5% in Wisconsin. The last major difference, therefore, is how much a typical person will drive each year. Minnesota is on track to lower its per capita vehicle miles traveled (VMT) by around 8%, to less than 9,000 per year. In Wisconsin, that number is holding steady at just under 10,000.  

A shift in any of these trends could push either state closer to, or farther from, achieving the much-needed reductions. Based on our analysis, 14 states are on track to lower emissions by 10% or more. This falls short of most targets, but it would be an important shift from past trends. That also leaves some states with even smaller reductions and around 25 states in which emissions could likely increase—some by upwards of 15%. 

Why aren’t more states on track? 

At the state and national levels, there is a heavy focus on electrification for achieving greenhouse gas reductions. The White House anticipates electric vehicles making up 50% of sales by 2030. The faster that transition happens, the fewer harmful emissions we will produce.  

However, recent reports suggest fewer than 1.5% of light-duty vehicles in the U.S. are currently electric. This is lower than even the most modest forecasts from several years ago and far lower than most low-carbon scenarios would call for. Federal incentives like EV rebates and the National Electric Vehicle Infrastructure (NEVI) program could help accelerate the transition, yet EV sales seem to be slowing 

That is why VMT is so important to consider and why, as we’ve written before, counting on electrification alone is a risky wager. Not only is every vehicle mile traveled associated with higher emissions and energy use, but helping people drive less can also save money and improve safety. A new calculator from RMI provides state-level estimates of these co-benefits. 

Our analysis suggests that while a handful of states could see fewer vehicle miles traveled in 2035, more states could see that number increase by at least 10%. World events like rising gas prices or another pandemic could push those numbers down, but something like widespread adoption of autonomous vehicles could cause it to skyrocket. 

What can states do better? 

Several studies point to the importance of cash incentives for encouraging a shift to electric vehicles, especially in the near-term. Findings show a $1,000 subsidy increases state-level registrations by at least 5% and a $1,000 rebate increase sales by 2.6%. Other research suggests nonmonetary mechanisms like a robust charging network, high-quality vehicles, and overall culture shift are more effective in the long-term. 

Every state is currently engaged in building out the nation’s charging infrastructure and many offer additional incentives for vehicle purchases. Unfortunately, even more states impose tax penalties for owning electric vehicles. These stopgap measures are intended to compensate for lost fuel tax revenues, but they can end up costing EV owners more than their fare share. Many are beginning to consider a VMT-based user fees as a more viable long-term solution, which could subsequently help meet long-term climate goals. 

In addition, state DOTs—along with legislators, sister agencies and local partners—can be leaders in moving toward more sustainable travel options, encouraging more efficient land use patterns, and ultimately helping to lower the amount that residents must drive to meet their basic daily needs. Late last year, we offered an overview of recent state-led climate initiatives and we are currently working with the Georgetown Climate Center to dive deeper and share more lessons learned from those leading by example. 

How we ran the numbers 

We compiled all the necessary data for the years 2000 to 2022 and developed forecasts in 2035 to estimate total greenhouse gas emissions. Our formulas and some of our basic assumptions are outlined by the U.S. Department of Energy. These include conversion rates for translating gas and power to carbon emissions. 

We first estimated vehicle electrification rates for each state using data from U.S. DOE. To predict future EV rates, we developed logistic curves (S-shaped curves that grow quickly at first, then level off as EVs approach 100%). We also estimated the emissions rates from electric power in each state using annual reports from the U.S. Energy Information Administration and projected those rates into the future using simple linear regression. Those two factors let us calculate average emissions per mile. 

We estimated total annual VMT from light-duty vehicles in each state using data from FHWA (Tables VM-2 and VM-4). The distribution of VMT by vehicle type (percent of VMT) is missing for some years, so we assumed the average value for each state from available data. We then calculated VMT per capita and projected those trends into the future for each state using linear regression.  

To estimate total emissions in forecasted years, we calculated the average emissions per capita and multiplied that by the expected population growth, which we estimated for each state using linear regression. 

The full set of data can be explored using our interactive dashboard. 

Photo Credit: Ryutaro Tsukata via Pexels, unmodified. License.