They come and go with less frequency now: empty trains across the country as this nation's public transit system finds itself in peril, with millions of Americans changing their commute routines because of COVID-19.

"Transit is definitely in trouble," said Jarred Johnson, who oversees the group Transit Matters.

It's not the empty trains and buses that bother Johnson so much as the proposed cuts on the horizon, as ridership nationwide has plummeted.

An estimated 36 million people across the country depended on public transit before the pandemic, but they just aren't riding right now, so revenues are down dramatically.

In Washington D.C., the Metro is losing nearly $100 million a month; New York City's MTA is facing $16 billion in potential cuts and San Francisco’s light rail is more than $33 million in the hole. Public transit lines in nearly every major city across the country are facing financial uncertainty.

"It’s really time for our political leaders to step up and provide the funding transit needs," Johnson added.

Another big concern is that if public transit services are cut now, they won't be there for riders when the pandemic is over. Used car sales are also booming with the average price of used vehicles up more than 9 percent, leading transit advocates to worry that some riders might be gone permanently.

"It’s not like people are choosing to not take transit on their trips, they’re not taking trips," explained Beth Osborne, with Transportation for America.

Osborne's biggest fear is that if cities and states cut public services, people won't be able to get back to work on the other side of the pandemic.

"I think we have to ask ourselves: do we want our economy to function or not?" Osborne said.