The thing about light rail is, you never know who'll board at the next station and what personal baggage they'll be toting.

If you're lucky, the stranger across from you will just smile, pull out a book and read.

If you're not, uh oh.

The person in the next seat may sing loudly and, chances are, off key. You may find yourself singled out as audience for some sad and confused life story. Or your seatmate may launch into a profane rant.

Regular riders know the preemptive measures. They bury their nose in their iPad, slip on earbuds and gaze out the window, or make like an ostrich and just close their eyes.

Then there is Brian Green.

Not that you'd notice him. He's the unassuming guy sitting over there with the neat goatee, pressed shirt, tie and slacks. For years, Green, 51, usually kept his head down during his 20-minute commute from Rosemont to downtown Sacramento, where he works at the state Senate.

Now he's looking for trouble. Or humor. Or pathos. Or, really, anything interesting to write about.

Green is light rail's self-chosen cultural anthropologist. BlackBerry in hand, he taps out short, on-the-spot reports to his 600-plus friends on Facebook.

His dispatches, now in the hundreds, are warm, witty, honest and gritty, and sometimes jaw-dropping. He and his wife, Sheila, recently compiled 200 of them, along with photos, in a self-published book called "Rail Tales: Adventures on Public Transit" (CreateSpace, $14.95, 102 pages).

He listens in on conversations. (After all, he says, the loud talkers seem to want an audience, or at least don't care who hears their business.) He asks strangers how they're doing. He even, on occasion, engages – cautiously – with the car's craziest character.

He's doing it, Green said, because what happens on light rail is too juicy not to share.

"You can't make this stuff up!" he said, grinning. "I'm trying not to be a voyeur. I just love to people-watch."

He writes about the woman who got so angry at her son that tossing profanities his way wasn't enough. So she opened a loaf of bread and threw slice after slice at him, Green reports, "with the rest of us sandwiched in the middle."

He tells of the ironic rebuke he got for watching as a man took off his shirt and a female friend rubbed cologne on his back.

"The train car now smells like the Macy's fragrance counter," Green wrote. "He notices ME staring at HIM and says, 'Please don't pay attention – this is PRIVATE.' "

What may make Green distinctive, though, is not just that he finds Sacramento rail interesting enough to write about.

It's his take.

Green is amazingly tolerant, even sympathetic. Sacramento Regional Transit, he says, is a petri dish of the human condition, where people from different worlds interact daily in close confines, and where private lives sometimes are on public display.

Green watched a man give up his seat to an older woman with a large package.

"Thank you sir. You're a kind man," she said. He responded, "No, actually, I'm NOT. I'm not a kind person at all. But I'm still lettin' you have my seat, lady."

Green's BlackBerry captures a vaudevillian quality to train life: "Two loud guys with probably four teeth between them (not judging, just observing), sharing Easter plans," Green writes. " 'Hey, I'm gonna go visit my old lady and my daughter down in Chinchilla!' 'You mean CHOWchilla, you fool!' 'Uh, yeah, I'm goin' there too!' "

Some of his posts will confirm suspicions held by non-riders that light rail is not where they want to be. There was the day a man on a cellphone snapped his fingers at Green and shoved Green's leg aside.

"I'm sitting here now," the guy said. "You ARE? I don't think so," Green snapped back. The bully backed off and sat elsewhere, but glared at Green. "It may not end well," Green posted on Facebook.

Then there was the day Green helped stop a beating. It left him shaken. His post:

"When a man is POUNDING a woman with his fist, ya gotta get involved. Security responded. SHE'S shaken but OK, I guess; HE ran off without his shirt, which I am now holding (and with police chasing him), and I survived with only a stepped-on shoe and an elbow in the gut.

"That'll teach me to leave work early."

Green, who has a radio background and is a communications specialist at the Capitol, loves the creative process. He's in a choir. He takes photos. This is his writing outlet. But his Facebook posts are more than a creative exercise. They are a defense mechanism.

Until he started his chronicles three years ago, Green said, he was among those who sometimes grumbled about rude behavior.

"Maybe there is a cathartic part of it," he said. "You are at the mercy of this crazy behavior. This is a way to cope with it."

Often, however, Green finds sweetness, humor, camaraderie and even mystery on board.

He describes a girl with a Tinkerbell backpack and princess umbrella snuggled up against her father, both asleep, rocking gently with the swaying train.

A woman is putting on makeup. She looks up from her mirror at Green and asks, "It's not helping, is it?"

Another day, the train just stops – no lights, no air conditioning. "Still sitting," Green writes. "And someone way in back yells out, 'I THINK ARNOLD JUST FURLOUGHED OUR DRIVER!' Total you-had-to-be-there laughing ensues."

Green once noticed these mysterious words scrawled in lipstick on the window: "Coco no longer loves Snowflake." He leaves readers to guess the back story.

"A lot of times, it is really nothing, but it's interesting," he said.

One woman, a stranger, pulls out photos of her grandchildren to show him. He oohs and aahs at the appropriate moments. As she leaves, she says, "Thanks for listening, pancake."

A term of endearment? "I'll choose to feel complimented until I'm told otherwise," he writes.

Friend Lynn Lorber, who also rides light rail, has asked Green: What is it about you that you get into these conversations with people?

"He's just engaging, I guess," Lorber concludes. "You feel his compassion."

Sheila Green said her husband seems to have a good antenna.

"I've been on the train with him and don't see what he sees until he points it out," she said. "I think it really is just the reporter in him."

Regional Transit operations chief Mark Lonergan said Green's stories reflect an onboard reality. Even though RT has a police force, live cameras, emergency call buttons and even some fare checkers, the agency cannot toss riders off trains simply because their behavior is annoying.

If a person is disturbing the peace or posing a physical threat, yes. If a person is rude or smells bad, no.

Lonergan said he wants to buy Green's book.

"Light rail is a melting pot," he said. "I've had some of those experiences too."

Green's postings reflect the exciting or interesting moments on light rail. But most rides are unremarkable, Green said. Weeks can go by between postworthy moments.

Green said he prefers that. His favorite light-rail moment, in fact, is a quiet Friday when he gets to wear his blue jeans and just relax.

He isn't searching for any cosmic meaning to light rail. It's just his daily ride. But he knows enough to know there could be a surprise around the bend.

"I just sat down on the train, sighed and leaned back." he writes, "and the woman next to me suddenly PUTS HER ARM AROUND ME and says, 'Honey, you look like I FEEL – like yer glad it's Friday!' "

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