All around Valerie Joseph, there is a fleet of Uber cars rolling by on New York City streets.

But though she could really use the ride-hailing app, Ms. Joseph said she does not bother because Uber has so few wheelchair-accessible cars to dispatch. “It’s plain unfair,” said Ms. Joseph, 41, who relies on a wheelchair.

Now, Ms. Joseph is part of a class-action lawsuit accusing Uber of discriminating against New York City riders with disabilities by providing scant access to wheelchair-accessible cars at a time when ride-hailing apps are becoming a common alternative to public transit in the city. The lawsuit was filed on Tuesday in State Supreme Court in Manhattan by Disability Rights Advocates, a nonprofit organization.

While Uber offers wheelchair-accessible cars through its UberWAV service, the lawsuit claims that these special cars, which typically have lifts and ramps for mobility devices, account for a tiny fraction of the 58,000 for-hire cars dispatched by Uber in New York City’s five boroughs. Moreover, this already limited pool of cars can be used for other riders, and vehicles may be unavailable when needed by those with disabilities, the lawsuit said.

The result is that “even when an UberWAV vehicle is technically available, because so few exist, there are typically frequent and lengthy delays,” the lawsuit stated. It added, “As such, people who use wheelchairs and use UberWAV must contend with missed appointments, being late for events and other stress and inconvenience.”