A report out Monday from the United Nations Intergovernmental Panel on Climate Change points to the need for monumental action to stop the most dire outcomes from a warming climate. Climate scientists say here in the United States, the transportation sector needs a lot of work — it’s the country’s largest source of carbon emissions.

Last week, Marketplace covered President Joe Biden’s plan to get more electric vehicles out on the roads. But there’s also a lot that needs to happen to get cars off the road, too — particularly expansions in public transportation.

Transportation makes up 29% of all greenhouse gas emissions in the U.S., and most of that comes from cars and trucks. People who rely on their cars need to have other options, said Elizabeth Irvin with the Union of Concerned Scientists.

“One of the things that’s really critical for folks feeling comfortable giving up a car is being able to have confidence that the transit is frequent and reliable enough to get people where they need to go on a daily basis,” she said.

In Ontario, Oregon, for example, Katalin Plummer is not able to get where she needs to go on public transit. She lives in a rural county, where cows outnumber people 5 to 1.

“It would be nice if I could just, you know, hop on the bus to go to work,” Plummer said.

But her town’s one bus doesn’t run frequently enough to make that viable. 

The infrastructure bill that’s before the Senate includes $39 billion for public transit to upgrade and expand bus systems, transit stations and rail.  

The White House stresses that this funding is in part directed at communities of color, especially since many of those communities both rely on public transportation and don’t have easy access to it. 

That is a historic investment in transit, said Adie Tomer with the Brookings Institution, but it’s going to take even more to convince people to change their ways, “not only to make sure they ride transit more but to use transit, as well as biking and walking, as an effective way to reduce all the climate impacts from all of our local transportation habits.”

And that, Tomer said, will take a much bigger investment.