“We want to see what impact this plan has for customers, and see what gains in productivity this accomplishes,” Thomas F. Prendergast, president of New York City Transit, said at an agency hearing on Monday.

The idea was met with guarded optimism from riders’ advocates on Monday. Some said that the plan made sense in light of the enormous growth in weekend ridership, which has doubled in the past 20 years.

But Andrew Albert, chairman of the New York City Transit Riders’ Council, said the changes could be “too severe on our travel patterns.”

“It is unlike anything they’ve done before,” Mr. Albert said. “It’s worth trying out, but if they see a drop-off in ridership, then you know this isn’t a good idea.”

Officials predicted that when a line in Manhattan is closed at night, riders could expect to add 10 to 15 minutes to their usual travel times. But many trains run once every 20 minutes during late-night hours, meaning a missed connection could result in a significantly longer commute.

Gene Russianoff, a staff attorney at the Straphangers Campaign, said he hoped transit officials would be careful in their evaluation of the project. He noted that while officials promised a reduction in “customer inconvenience,” they did not specifically promise fewer weekend disruptions over all.