John Dahl knows the secrets to making a great B-grade fright flick: 1) don't take yourself too seriously and 2) what you don't show can be much more terrifying than what you do.

The director of such sublime human underbelly fare as "The Last Seduction," "Red Rock West," in "Joy Ride" Dahl takes two teen movie staples -- the road trip and the psychotic killer -- and marries them in one dark, fun and scary popcorn flick.

College boy Paul Walker ("The Fast and the Furious") and his knavish, drunk-and-disorderly brother Steve Zahn ("Saving Silverman") are travelling home for summer vacation when they prank a trucker on the CB radio in their beater of a used car. Walker puts on a girly voice and tells a creep using the handle "Rusty Nail" to meet him in a motel room for an anonymous late night tryst.

But Rusty Nail don't take none too kindly to being tricked. He rips the jaw off the blameless guy in said motel room -- while our heroes listen, paralyzed with fear, from one door down. Now the trucker is in hot pursuit of Walker and Zahn, planning to scare the hell out of them -- because, well, turnabout is fair play -- and probably kill them as well.

Of course, they don't realize they're being tracked until Rusty Nail comes over the radio the next day saying, "You really should get that fixed." Thinking they're being toyed with, Zahn says, "What?" And after an eerie pause, Rusty replies in a raspy whisper, "Your...tail...light."

Yikes!

Dahl does a fantastic job of building tension throughout the picture, from the muffled screams coming through the thin motel room walls to the way he jumps your heart into your throat when an anonymous big rig pulls in behind the brothers at a remote gas station in the middle of the night. Dahl's distinctive sense of cinematic showmanship adds to the frenzy as well, with most of the film shot in motel neon or tail light red hues.

As Walker and Zahn are blinded by high-riding headlights bearing down in the rearview mirror, they get chased onto dead end frontage roads and pursued into cornfields where they desperately scurry for cover on foot while Rusty Nails plows through frighteningly close behind in his monstrous 18-wheeler cab.

Then just when the boys think they've lost their tormentor, they stop to pick up Walker's conspicuously braless (it is a trashy movie after all!) hometown sweetie (Leelee Sobieski) from another college, and the radio crackles ominously back to life with a foreboding breath: "Who's the pretty girl?"

Double yikes! Things are about to get a lot scarier.

"Joy Ride" packs a few awesome twists that help you to buy into the fact that this trio doesn't just turn off the CB and floor it all the way home. It helps too that they're smarter than the halfwits who populate of your typical horror movie. Walker does try to level with the local sheriff and does try to reason with Rusty Nail.

But besides being a genuine white-knuckler -- thanks to surprisingly solid performances and Dahl's deft visual and psychological manipulation -- this picture's best asset is its dark sense of humor. Zahn's tendency to ham it up comes in handy here, playing the perpetrator of the prank that gets everybody into this mess in the first place. Comic relief comes as a surprise in some of the movie's tensest moments, too -- like when Zahn rescues Sobieski from a gang of molestation-minded rednecks by acting like a jealous wife-beater who thinks his woman is flirting behind his back.

After 90 minutes of cagey execution, though, Dahl disappoints a little with one of those tiresome not-really-dead-yet finales. If you care to pick nits (I can't help myself), there's also a dozen or so irritating geographical and logistical faux pas (it doesn't take three days to drive through Wyoming) that would have been so easy to fix it makes them hard to forgive.

None of my complaints, however, are serious enough to put the breaks on this great guilty pleasure of a killer road thriller.