At one end, a group of men has gathered. Few ever pay them much mind, but the longer you look, the more they stick out, because they have been at the train station for a very long time, though they have nowhere to go.
They are members of a network of railroad fanatics -- hobbyists who study trains, photograph trains, videotape trains and ride trains, all with a fervor that makes birders, ham radio operators and the like seem like laggards.
Dropping in here helps one understand a confounding issue raised by the Sept. 12 Metrolink crash: why a group of teenagers had been exchanging text messages that day with engineer Robert M. Sanchez.
It turns out that the teens were fledging members of this network, a world that is virtually unknown except among the enthusiasts themselves and the engineers who offer them a tired wave at the station. But there are hundreds of thousands of them -- across the United States, in India, Australia, Zimbabwe -- hobbyists who are known, variously, as railfans, cranks, trainspotters and gunzels.
The most die-hard are known as foamers -- a term believed to have originated as an insult, used to describe people who get so excited at the sight of a train that they foam at the mouth.
Some refuse to use the word "foamer." (These are sensitive people and not without reason; in England, "trainspotting" is a euphemism for useless activity.) Others have appropriated the word for themselves, an exercise in a kind of geek pride.
Whatever they call themselves, they seem to speak in a foreign language -- of wigwags and hoggers, shooters and boomers, varnishes and highballs. Some speak elegantly of the rails' role in the development of the West. Many speak of trains with reverence, not as a means of transit but as a rolling metaphor. Train travel, they believe, fosters a sense of community and cooperation sorely missing in today's world -- certainly on the freeways of Southern California.
At its heart, the hobby has the simplest of foundations: the might and majesty of the machines themselves. The enthusiasts see what most do not: tons of steel ferrying businesspeople, toys from China, huge tanks of natural gas, all sharing the same space without incident -- except for those rare, terrible moments when the whole thing falls apart.
"The power is just so immense," said Scott Zechiel, a software engineer, standing on the Fullerton platform.
Behind him, train after train rumbled in, each its own beautiful mess, all bellowing engines and hissing brakes. The largest of the trains, typically the freights, cast off enough of a breeze that everyone's hair puffed up a bit as they passed.
"We like it when the ground shakes under our feet," Zechiel said. "We like the sounds, the screeches. We can't get enough of it. So we keep coming back."
In Southern California, Fullerton is foamer central.
The station is friendly to railfans -- which is not true of some others -- and is pleasant and comfortable, with shade canopies and cafes. But mostly it's about the traffic; some days 100 or more trains pass through, and it's an unusual blend of passenger trains and freights.
Most of the teens who knew Sanchez were Fullerton fixtures. They were often seen racing down the platform, cameras and tripods over their shoulders, to get the best shots of an oncoming train. Indeed, one of the first places several of the friends went after the crash was to the Fullerton station, where they could clear their heads and be with their own.
Zechiel, 44, is another regular. He bought his home in nearby Yorba Linda largely because it overlooks the tracks. Since 1997, with an informal group that calls itself the Fullerton Foamers and Foto Society, Zechiel has spent every Friday and Saturday night watching the trains. He figures he misses about four weekends a year, when he's sick or when he is traveling -- "which is, of course, by rail," he said.
On busy nights, there are five or six similar gatherings of railfans at the Fullerton station, sometimes as many as 50 railfans in all. Engineers have taken to calling it "Foamerton."
The FF&FS, as Zechiel's group is known, is tight-knit and well-organized. Members bring scanners to listen to conversations between engineers and conductors and a laptop programmed to replicate what dispatchers see at their desks. Many members are published photographers; during lulls between trains, they show slides of trains set to the music of Moby and U2.
Together, they make regular trips to the Cajon Pass, a popular gathering place for train lovers because of dramatic backdrops and track assemblies considered to be engineering feats. One trip, each January, is called "The Big Cajona"; they camp out with a luau theme.