The opening of the Second Avenue line and its ornately decorated stations in January was a high point for the agency, but the signal system — the least visible yet perhaps greatest challenge of all — remains mired in an analog era.

20 dating  new service york-65

The London Underground, known as the Tube, opened in 1863 and is the oldest subway system in the world.

It now carries about five million people each day, its highest ridership ever.

It took about a decade to complete the signal network on the L line, and work on the No. Confronted with infrastructure dating to the 1930s and a vast system of 472 stations (the most of any subway in the world), officials are forced to decide which projects to prioritize with limited financing.

The transportation authority asked for $3.2 billion for signal and communications work in its latest five-year capital proposal — about 10 percent of its $32 billion budget request — but $400 million was cut from the plan approved by state leaders last year. Cuomo, a Democrat, like the mayor, was focused on finishing the first segment of the Second Avenue subway on time, but critics say he has shown far less urgency about the deteriorating condition of the subway’s signals.

“We have to find a way to shorten that.”New York’s more than century-old subway has been essential to the city’s growth, but there is increasing alarm that after years of progress, the system is sliding backward.

To accommodate the nearly six million riders who take the subway on weekdays — the highest level since the 1940s — the authority is spending billions of dollars on new stations and more spacious trains.

Worsening subway service is one of the many infrastructure challenges confronting the region, including recent commuting upheavals at Pennsylvania Station in New York. New York’s quest to install the new system began in 1991, after a subway derailment at Union Square in Manhattan killed five people.

Amtrak, which owns the station, plans to close several tracks for repairs that will disrupt service this summer on New Jersey Transit and the Long Island Rail Road, two of the nation’s busiest commuter railroads. The train operator was speeding after he had been drinking.

State and city leaders feuded over the agency’s current capital plan for a year, and the agency still does not know how Mr.