It's a dangerous job: You're surrounded by live electrical wires, dangling 30 feet in the air, and dodging oncoming trains - and that's in a single shift.

You're trying to prevent a catastrophe, be it from a flood, an explosion, or a mechanical failure.

Does that sound like the SEPTA we know, sometimes love, and occasionally hate?

That's the SEPTA that will be shown tomorrow night on the National Geographic Channel's "World's Toughest Fixes." A special premiere for city bigwigs was held last night at the Comcast Center.

"A common question I've gotten is why SEPTA," host Sean Riley said yesterday, pre-premiere. "The answer is, there are a lot of other transit systems, but this is one of the largest and unique in that there are many modes of transportation under one umbrella . . . It was an opportunity to look at an entire transit system as an organization that keeps the blood of the city pumping."

Forget the uninterested token clerks and the occasionally comedic train announcers. SEPTA has 9,000 employees handling 2,200 square miles of tracks, and this is serious - and sometimes dangerous - stuff.

The show, now in its third season, usually features Riley as he joins crews that repair things such as nuclear turbines, Alaskan oil pipelines, and ski lifts.

The SEPTA show - titled "Philly Mega Transit" - features multiple projects intended to show the round-the-clock nature of SEPTA's work.

There's Riley in the morning with "the wire train," working around live power lines and warning his sound man to keep the boom down or risk death.

There's Riley in the late afternoon with the wire crew, "SEPTA's cowboys," he calls them, as they climb high up poles and work while hanging over the tracks.

There's Riley in the middle of the night with the track maintenance crew, cutting and laying new rail by hand.

Spokesman Richard Maloney said SEPTA was thrilled to showcase its workers on national television.

"I've been dying to get someone to look at how things work," he said. "Day to day, the media look at how things don't work. It's a mark of pride how proud our people are to show the world what they do. This is their moment in the sun."

The hour-long show is made to appear as if all of the action takes place over a two-day span, but film crews actually spent more than a month working with SEPTA.

There's some hype, such as when a team armed with a bomb-sniffing robot deals with an unattended red suitcase left on a train. Quick video of past subway bombings - Madrid 2004, London 2005 - flash on the screen.

It turns out the whole thing's a routine practice for the crew, who note that 99 times out of 100, their one-of-a-kind robot is unleashed on someone's dirty underwear or their midday meal.

Another would-be nail biter occurs when a train reports a problem with its automatic train control system. Go to footage of last year's Washington, D.C., Metro collision between two trains, which killed nine people.

But this train is safely brought in and, almost just as quickly, repaired.

Still, even with some faux drama, it's an interesting show. It gives viewers a behind-the-scenes look at the subway's "money train," which makes quick stops in every station so employees can retrieve coins and cash, and the "vacuum train," upon which employees work cleaning underground rails while most of the city sleeps.

In one segment, Riley cuts a replacement rail incorrectly. The supervisor has to come in and trim it to fit it into place, joking that it's not, "measure once, cut twice."

"The work that goes on down there is not only difficult and loud and dark and lonely, but also at the same time precise," Riley said.

Maloney said that between the photography and the on-screen graphics, viewers will get a fairly clear picture of what SEPTA employees do.

"They took something extraordinarily complex and they got it right," Maloney said. "This is unprecedented in the industry."