Sen. Ben Cardin announced Monday that he won’t seek reelection, taking with him his significant advocacy for transit, biking and walking programs just as President Joe Biden’s climate initiatives are beginning to ramp up.

While Biden’s focus has been on pushing America toward zero-emission vehicles, Cardin has sought to reduce single-occupancy driving altogether. Until this year, he chaired the Senate Environment and Public Works Committee’s panel on transportation, where he fought for big increases for biking and walking, as well as a new program for helping rebuild communities impacted by highway construction included in the 2021 infrastructure law.

“Without your stalwart champions on the inside, you’re not going to get very far,” said Kevin Mills, vice president of policy at Rails-To-Trails Conservancy, which advocates for biking and walking infrastructure. “He helped put us in a position to succeed going forward.”

Cardin fought to revive work on Baltimore’s Red Line after then-Maryland Gov. Larry Hogan canceled it. He helped ensure that the Reconnecting Communities program, to rebuild street grids that have been bisected by highways, was included in the 2021 infrastructure law. And he has been a key champion for a federal program funding biking and walking infrastructure since its inception.

His work to undo the harm caused by highway construction was inspired in part by another former Maryland senator, Barbara Mikulski, who came into politics through the fight against highway expansion in Maryland.

The $1 billion reconnecting communities program Cardin championed was one of the most talked-about new elements of the infrastructure law. Forty-five communities received grants under this program earlier this year.

Biden had originally sought $20 billion for that program. Advocates will miss Cardin’s presence when it’s time to reauthorize, and possibly increase, the program in 2026.

Caron Whitaker, deputy executive director of the League of American Bicyclists, said Cardin was instrumental in bringing Republicans on board to support a program that shunts part of federal highway dollars to pay for biking and walking infrastructure, during a time when House Republicans wanted to eliminate the program altogether.

Instead, Cardin led a bipartisan rebranding of the program under the banner of local control. “He reached out and he wanted to find a way to make sure that we could still get some funding down to local governments and to spend on biking and walking,” Whitaker said. “He’s a regular bicyclist himself and he’s seen how it’s helped his communities in Maryland, and wanted to make sure that the funding was still available.”

“He was really good at making this a bipartisan program,” she added. “We’ll miss having him in the Senate.”

Cardin helped re-build support for biking and walking and managed to secure a 70 percent increase in funding for those programs in the infrastructure law, according to Rails-to-Trails,with new policies to ensure that the money was used for its intended purpose.

Senate EPW Chair Tom Carper (D-Del.) has been a partner to Cardin on many transportation initiatives, including the need to increase or replace the gas tax with a more sustainable alternative. But Carper, who is 76 years old, has not yet announced whether he plans to run for reelection in 2024.

Despite his departure, advocates for alternative transportation means say Congress still has plenty of advocates for transit, biking and walking, including Sens. Ed Markey (D-Mass.) and Jeff Merkeley (D-Ore.) who remain on the EPW transportation subcommittee, and the junior senator from Maryland, Chris Van Hollen.

In the House, Rep. Rick Larsen (D-Wash.) now leads the Democrats on the House Transportation Committee with a keen interest in transportation sustainability and equity, and Rep. Earl Blumenauer (D-Ore.), never without his neon bicycle lapel pin, is also a reliable advocate for those issues.

“I want to be optimistic,” said a Cardin aide who was granted anonymity to speak according to office policy. “There is enthusiasm for electrification and cleaner vehicles, but there will need to be a continued push for walkability, bike and pedestrian safety and alternatives to driving.”