The Environmental Protection Agency said Monday it will tighten pollution standards for cars and light trucks in an attempt to reduce carbon dioxide emissions from automobiles.

Why it matters: Transportation overall is the largest source of U.S. greenhouse gas emissions, so tougher standards for passenger vehicles are a major part of efforts to curb CO2 output.

By the numbers: The new rules will require passenger vehicles to travel an average of 55 miles per gallon of gasoline by 2026.

• The EPA said this new standard will prevent around 3 billion tons of greenhouse gas emissions by 2050, which it said is equivalent to more than half the total U.S. CO2 emissions in 2019.
• The rules will go into effect 60 days after it is published in the Federal Register.

Thought bubble, via Axios’ Ben Geman: The standards through the middle of the decade have been a long and winding saga. Former President Obama initially set them, but they were then weakened by former President Trump.

• Now Biden is restoring that effort with regulations […]