In a subway system that is bursting at the seams with its highest ridership since 1948, the G line has been a part of that surge. About 150,000 riders use the G line on weekdays, an increase of about 17 percent since 2010, according to the transportation authority. But it is dwarfed by the nearly 225,000 riders who take the crowded L line under the East River each day.

Mayor Bill de Blasio’s administration is betting that demand for public transit along the Brooklyn-to-Queens corridor will continue to grow as it moves forward on a $2.5 billion waterfront streetcar that would extend even farther than the G train, from Sunset Park in Brooklyn to Astoria in Queens. The ambitious — and contentious — project is at the top of the mayor’s transportation agenda, though it would not open until 2024 or later.

When the L train tunnel under the East River shuts down to repair damage caused by Hurricane Sandy, subway officials hope many riders will switch to other lines like the G, where they plan to add service and upgrade the Court Square station in Queens with two new stairways. Commuters who rely on the L line could take the G train to Queens and transfer to another line, like the No. 7 train, to reach Manhattan. About two years ago, the G subway tunnel between Brooklyn and Queens closed for storm repairs for five weeks that were painful for people who relied on the line.

In recent years, the unpredictable line has become more dependable, riders say, especially on weekdays.

“It sort of has a bit of a bad rap,” said Lisa Vanterpool, 31, of Queens. “Late at night, I try to avoid it, but during the day commuting to work, I find it to be pretty reliable.”

Ms. Vanterpool, who works in advertising in Brooklyn, said she might even miss the so-called G train sprint across the platform to board the line’s trains that are too short for its platforms.