For some it's the stains. For others it's the smell. But for many who avoid sitting on BART seats, it's simply a matter of the unknown.
What actually lurks underneath those mysterious blue -- mostly -- seat cushions on BART?
A study by the Bay Citizen March found all sorts of bacteria hiding in the seats, including some of a drug-resistant variety.
The agency took notice and admitted cleanliness has not been its best trait in recent years as BART has focused more on security.
But BART is trying to do something about the problem. The agency is planning on spending $2 million in the near future to replace some dirty seats.
And the transit agency is also working on its trains of tomorrow. Wednesday the public got another look at what future BART trains may hold.
In May, BART began conducting seat labs, where riders can give feedback on what they would like to see train seats look like and sample a few that BART is contemplating installing at the same time.
Wednesday BART held a lab at San Francisco State University's campus, where the school has a free shuttle driving students between the university and the Daly City BART station.
"I see this as a fantastic opportunity to actually look at a number of different designs," Janet Abelson, chair of BART's Accessibility Task Force, said in a statement. "It's been a really long time since BART has had an opportunity to update and upgrade the seating."
The labs are BART's way to get feedback as the agency looks to replace the nation's oldest transit cars.
The next chance riders will get to see what future BART trains may look like is May 18 at the Pleasant Hill/Contra Costa Centre BART Station, between 11 a.m. and 3 p.m.