BART is being sued by advocates for the disabled, decrying elevators they say are too often broken or unsanitary.
The class-action lawsuit was filed in federal court on Wednesday.
It does not seek any monetary damages, just improved maintenance and supervision of the station elevators disabled riders rely on.
"For us, it's more than an inconvenience, it affects our health," plaintiff Pi Ra told KTVU.
Decades of diabetes has left Ra with broken bones in his feet that won't heal.
The pain is aggravated if he standing too much.
Bruises, blisters, and open wounds are a constant risk.
But unreliable elevator access often forces him to walk further.
And he admits he enters every elevator cautiously, in case the floor is soiled with urine or feces.
"I look to see what's going on so I know where to move my feet and my bicycle to miss anything that might be deposited," said Ra.
Homeless people use the elevators, and escalators, as bathrooms.
It is a constant problem for BART maintenance, but the disabled say the transit system needs to do more.
"It's very gross and happens very frequently," Rachel Langston told KTVU.
Langston is an attorney with Legal Aid at Work, and has navigated BART for ten years on a motorized scooter.
"I see puddles of urine and other human waste," she described, " and you can't avoid it in a small space, and it's really disturbing to track it arond with you as you go about your day, it's dehumanizing."
Finding elevators out-of-service is another chronic problem, critics say.
"Just today, seven BART elevators were out, they were warning on their website, it was seven, and that means people just can't get from place to place," observed Rebecca Williford, with Disability Rights Advocates.
BART says it share the frustration, and is spending millions of dollars to improve escalators and elevators, including splashguards, and easier-to-clean floors.
In response to the lawsuit, BART issued a written statement acknowledging that "hardships can occur" but blaming "the impact of the homeless crisis" and noting it has "hired more crews and offered overtime" for more cleaning.
BART was sued over the same issues almost twenty years ago.
As a result, maintenance improved, but watchdogs say it has now regressed, and the system is older, and even busier than before.
Ra, who rides daily between Concord and San Francisco, doesn't believe BART gives disability access high priority.
"They'll talk about a shortage of maintenance people, but they have money, they have ways of doing it," he declared, "if it's really important to them".