Most U.S. cars and trucks churn out several times their weight in greenhouse gases every year — and that’s a lot of gases. Add those molecules together, and cars and trucks are to blame for about two-thirds of greenhouse gas emissions from the U.S. transportation sector. As more cars and trucks hit the roads, this pollution will increase dramatically unless strict emissions-reduction and fuel economy policies are in place. The Center makes it our job to ensure these policies get there and stay there.


In the wake of the oil embargo and the passage of the 1975 Energy Policy and Conservation Act, U.S. vehicle fuel economy improved substantially in the late 1970s. More recently, however, fuel economy has stagnated and even regressed at times as automakers have peddled ever larger, more powerful and more gas-guzzling sport utility vehicles and pickup trucks to Americans. Thankfully, in November 2007 the Center and our allies prevailed in Center for Biological Diversity v. National Highway Traffic Safety Administration, a major lawsuit filed against the Department of Transportation for failing to properly account for greenhouse gas emissions when setting unreasonably low national fuel economy standards. In December 2007, Congress mandated an increase in fuel economy to 35 miles per gallon for all passenger vehicles by 2020: a change for the better, but clearly not where we need to be.

In 2008 the Bush administration released a new proposal for fuel economy standards that were slightly better but still far too low; they were determined through a fatally flawed analysis employing numerous assumptions defying common sense and the law. The Center filed comments against the proposed standards, and our opposition was even echoed by the Environmental Protection Agency, which said the administration’s analysis brought up environmental concerns and contained inadequate information. On the same day the Center filed comments against the proposed standards, the Ninth Circuit Court of Appeals denied an administration request to revisit the court’s November 2007 ruling in our case against the Department of Transportation, once again affirming that fuel economy standards must be set at the maximum feasible level to save oil, reduce greenhouse gas pollution and protect consumers.

In January 2009, the Bush administration announced it wouldn’t finalize its fuel economy standards before it left office — but in March, instead of improving on Bush’s pathetically low standards, the Obama administration announced that its own standards would be about a mile per gallon lower. Less than a week later, the Center filed suit to overturn them, and in summer 2010, the administration announced its intent to increase fuel economy standards for cars and light trucks, with the most ambitious proposal raising them to about 37 miles per gallon by 2017. Standards for medium- and heavy-duty trucks were finalized in August 2011 and for passenger vehicles and light trucks in November 2011 —  both baby steps forward, far short of what’s technologically and economically feasible.

We also successfully challenged the Bush administration’s denial of a waiver required under the Clean Air Act for California to implement its 2002 Clean Vehicle Law (also called the Pavley Bill), whose goal is to reduce greenhouse gas emissions from automobiles sold in California by almost 30 percent by 2030. After two years of legal efforts by the Center (represented by the Western Environmental Law Center), California, 13 other states and many other conservation groups, in June 2009 the Obama administration’s EPA issued the waiver. An additional dozen states were also authorized to implement California’s law.

In August 2012 standards were finalized that mandated reaching maximum gas mileage of 54.5 miles per gallon by 2025. But once various credits and “flexibilities” are accounted for, the estimated mileage drops to about 47 miles per gallon. Cars are commercially available today that meet and exceed this standard.  

In 2020 the Center and allies sued the Trump administration to block a major rollback of fuel-efficiency standards for automobiles. The revised standards will worsen dangerous levels of air pollution and greenhouse gas emissions and cost consumers more at the gas pump without making the nation’s roads safer.

There have been changes for the better, but they're not good enough. The technologies currently exist to dramatically increase our fuel efficiency today to as high as 45 miles per gallon — and we must take advantage of these technologies in order to reduce atmospheric greenhouse gas concentrations to 350 parts per million and prevent climate catastrophe. We urgently need to transition to hybrid, plug-in hybrid and electric vehicles powered by renewable energy.

Exhaust pipe photo by Steevven1/Wikimedia