The Metropolitan Transportation Authority discriminates against people with disabilities because of its widespread lack of elevators and electric lifts in the subway system, rendering it significantly more inaccessible than other cities with large public transportation systems, according to two lawsuits filed on Tuesday.

The plaintiffs, a group of disability organizations and disabled residents who brought the lawsuits as a class action in state and federal court, say that the city’s subway system is one of the least accessible public transportation systems in the United States, with the lowest accessibility rate — 24 percent — among the country’s 10 largest transit systems.

More than 75 percent of the city’s 472 subway stations do not have elevators, lifts or other methods that make them accessible for people who use wheelchairs, mobility devices or are otherwise unable to use stairs. Of the approximately 112 stations that are designated as wheelchair-accessible, only 100 currently offer working elevator service for passengers traveling in different directions, the lawsuits charge. (The MTA said that 117 of its stations are accessible to people with disabilities.)

The lack of elevator service in the city’s subway system has been a longstanding problem. Michelle A. Caiola, the litigation director for Disability Rights Advocates, which is representing the plaintiffs, said the legal challenge comes after many futile attempts to achieve a resolution with the transit agency.