What distinguishes the new suit is that it seeks a definitive ruling about whether the ADA applies to Uber and similar companies, said Access Living attorney Charles Petrof.

"Once this is resolved with Uber, the rest of the industry will have to follow," he said.

The ADA contains an exemption for taxi companies on wheelchair-accessibility rules, but such requirements do apply to cabs in Chicago due to a local ordinance, Petrof said. Advocates tried but failed to push through provisions that would force Uber and similar companies to meet the same city requirements.

If Uber isn't a cab company it could be subject to the ADA requirements, but if it is, the Chicago ordinance could apply, Petrof said.

Uber does offer a service called UberWAV, which allows would-be customers to locate vehicles with ramps or lifts. But Thursday's suit says Uber's mobile map frequently indicates that no such vehicles are available anywhere in or near Chicago.

In an attempt to demonstrate how hard it is for disabled people to utilize Uber, the suit cites data that Uber provided nearly 2 million rides in Chicago in June of last year alone. But it says Uber gave just 14 rides to motorized wheelchair users over a four-year period starting in 2011.