The erosion of riders on public transit systems follows two decades of strong growth between 1995 and 2015, said Art Guzzetti, a vice president at the American Public Transportation Association.

“Rail was truly in a renaissance period and cities were coming back along with it,” Mr. Guzzetti said.

The recent loss of rail riders is linked largely to problems with reliability and a struggle by transit agencies to keep their systems in good condition, Mr. Guzzetti said. But rail is still the most efficient and affordable way to whisk people around dense cities.

“It’s good to have options,” he said. “Nothing is going to have the affordability of transit.”

In less than a decade, Uber and other ride-hail companies have transformed the transportation networks in cities across the country. Their growth has been so robust that by the end of this year, taxi and ride-hail trips are expected to surpass local bus ridership for the first time, according to a new report by Bruce Schaller, a transportation expert.

Taxis and the for-hire vehicle sector are expected to grow to 4.74 billion trips by the end of 2018, growing past the projected ridership on local bus services of about 4.66 billion trips, according to the report. Mr. Schaller said the move toward vehicles created a long-term risk “that neighborhoods are simply overwhelmed by traffic volumes and become less desirable places to live, work and do business.”

Uber, which successfully fought off an attempt by Mayor Bill de Blasio to introduce a vehicle cap in 2015, is on the defensive during its latest battle with the City Council. The company’s central argument is that New Yorkers need Uber more than ever since the subway is in crisis.

Uber’s leaders have also highlighted its car pool option, known as UberPool, and supported congestion pricing — a proposal to toll vehicles entering Manhattan’s busiest areas.