The Number 7 train is number one, according to the Straphangers Campaign's 12th annual State of the Subways report.

The report released Wednesday finds the 7 line ranks first among all 21 subway lines ranked.

Corresponding the group's MetroCard rating scale to a monetary scale of $0 to $2.25, a ride on the 7 is worth $1.55.

The survey finds the 7 performs above average in five of six categories, including frequency of service, regularity of service, delays caused by breakdowns, seat availability and car cleanliness.

The L line, which was top-rated last year, slipped to second with a MetroCard rating of a $1.50. But it is the cleanest line, with just 2 percent of cars had moderate or heavy dirt.

Both the L and the 7 have their own general managers who are responsible for their individual lines.

"I would give a lot of the credit to the program," said Gene Russianoff of the Straphangers Campaign. "I think having a person who you can email and say, 'There's been this lake at my station for the last six months, and it always fills up, someone better fix it,' makes people feel that they have a better chance of getting better transit."

Riders of the 7 line were also pleased with the line.

"It's reliable. They come frequently," said one.

"I'd say it's definitely the best line in the whole transit system," said another.

The C was ranked as the worst subway line, with a MetroCard rating of only 50 cents. It finished at the bottom of the pack in the categories of car breakdowns and was below average in all five other measures.

"Anyone who's taken the C knows the ancient cars that are on that line, and it provides a low level of service," said Russianoff.

Overall, the survey found the car fleet breakdown rate has gotten worse, with breakdowns happening nearly 10 percent more often.

About 77 percent of V train riders have the best chance of getting a seat at rush hour, compared to just 24 percent on the L.

While the 6 train has the most frequent service, running every 2.5 minutes at rush hour, the M runs only every 10 minutes.

Subway announcements and car cleanliness have improved over the past year.

The F train was the dirtiest line, with 20 percent of cars having moderate or heavy dirt.

City transit officials said they sought to improve service through rider report card surveys, and said systemwide reliability will improve as more new-model subway cars are used.