NEW YORK - The A train reached the end of its run in northern Manhattan shortly before midnight, but a 68-year-old man stayed on.

With a blank expression on his face and a plastic bag with a few belongings at his side, the man sat in a corner seat, motionless, waiting for the train to pull out and head south.

Another long night of riding the train to nowhere.

"I don't want to go to a shelter," he said, refusing an offer from the Police Department's Transit Bureau's Homeless Outreach Squad.

"They've got thieves and murderers there. I did that once - I don't want to go through that again," said the man, increasingly agitated, adding that he has called the subway system home for two years.

No one is sure exactly how many hard-core homeless live on the trains, in stations or in filthy, dangerous subway tunnels.

Police estimate fewer than 1,000 - but another group recently said it identified nearly twice that many last year.

Those numbers typically rise as the weather gets colder and more people seek refuge underground.

Help rejected

Most of the hard-core subway homeless regularly refuse offers of assistance from police or social workers, such as going to a shelter or taking part in a substance abuse program.

"There are some people who just don't want to be bothered and don't want to leave the system," said Cynthia Wilson, a program manager for MTA Connections, an outreach program run by the Metropolitan Transportation Authority.

"It's not illegal to be homeless," she said. "If you are in our system, have paid the fare, don't violate the rules and regulations, you can stay as long as you want. The hope is that, over time, you will be able to engage them and get them to accept services. It's a matter of building trust and familiarity."

That's a tough mission for the Police Department's transit outreach squad.

On a recent overnight shift starting at the A train's 207th Street terminal, Officers Tom Borroni, Solomon Land and Jim Walker walked through idle trains just before midnight, approaching those who appeared homeless.

A city bus waited on the street to take to a shelter those who were willing.

'I have problems'

Some denied being homeless, such as a woman sitting alone, a wool cap pulled down to the top of her eyelids. Clutching a cart stuffed with bags and clothes, she lifted her head slowly, insisting she had missed her stop - although she couldn't name which one.

Moments later, a man missing several teeth and wearing ripped jeans said he planned to ride the trains till it was time to go to a construction job in the morning.

"I have problems at home right now," explained the man, who said he was 51 years old. "It's no big thing."

Such subway riders "can be very frustrating," Borroni said.

"They just refuse any kind of help. And it doesn't make for a good environment for someone who is going to work, who gets on the train at 5 in the morning," he said. Because of that, one rule that typically is enforced prohibits anyone from reclining across several seats.

After 90 minutes of work, the officers persuaded only two of 20 men and women they approached to accept help - an average night for an evening with moderate temperatures. Throughout the subway system, police outreach units transported homeless riders to shelters, hospitals, substance abuse centers or other facilities 3,646 times last year.

It's common for police to help a homeless rider get to a shelter, then see him riding the trains the next night.

"There's got to be a better way," said Jeff Bell, 42, who quickly accepted the officers' offer of a ride to a shelter. "I'm tired. Maybe if I get off the beer I can clear up my head [and] do something for myself."

Sitting with another man who also wanted to be taken to a shelter, Bell said he was 42, but looked worn for that age. Scars crisscrossed his face, and his teeth were crooked. He was carrying the only possessions he wasn't wearing: a pair of sneakers.

Beer and trains

Bell said he had lived in a Brooklyn housing project but left because of drug dealing and violence. He also quit a job in a gas station and now makes small change redeeming discarded cans and bottles he collects.

"Every day I do the same thing: beer, beer, trains, trains," he said.

Outreach squad members who patrol the hardest-to-reach spots sometimes find long-abandoned storage or maintenance rooms in the tunnels turned into crash pads.

To deter the homeless from returning to the subway system, the police and the Transit Authority have boarded up many open areas, Sgt. William O'Leary said.

Tunnel dwellers sometimes are arrested and charged with trespassing.

Home for 17 years

Because of those efforts, officials said, the number of homeless killed on the tracks dropped to three in 2001 from 79 in 1989.

There were far more underground homeless back then - an estimated 5,000 people, partially a result of the crack cocaine epidemic.

Borroni said he recently found a man in a room off a tunnel in lower Manhattan who claimed to have lived there for 17 years.

The home had a mattress, a sofa and a television set rigged to a subway power source. Racy posters covered the concrete walls. The man's clothes were in a neatly folded pile.

The man told Borroni he had a job washing dishes but couldn't afford rent.

Not far away one recent morning, a police outreach squad opened an emergency exit on a traffic island on Houston Street near Elizabeth Street.

A wave of foul air rushed from the blackness below.

High-powered flashlights revealed that several people were living there, taking refuge on a stairwell passageway leading to F train tracks.

Next to a black plastic bag full of clothes, two umbrellas stood in a corner. Jugs of water, candles and a plastic bottle of European Mystique Hand and Body Gel were lined up on a set of steps.

Another landing was furnished with a rolled-up futon mattress covering a pile of clothes and two milk crates turned upside down, as well as a broom and a pair of liquor bottles.

On other landings, cops found a rug, a soiled blanket, more clothing and a newspaper.

The outreach unit had been here before - and workers had cleaned out the space. But the homeless, who make their way along a catwalk from one of two nearby subway stations, keep coming back.

"They want to be left alone," O'Leary said. "If you go repeatedly, you're disrupting them - it's not a comfortable place for them to be anymore."