WE'VE BEEN DOWN THIS HOLIDAY ROAD BEFORE.

Byline: Bob Strauss Film Critic

HIGH PRICES at the gas pump are nothing compared to the cost-per- laughs ratio in ``Johnson Family Vacation.'' It's a road trip comedy that goes halfway across the country before it runs into a couple of decent jokes.

This is, essentially, Cedric the Entertainer rehashing Chevy Chase's National Lampoon franchise. The difference here, besides the obvious substitution of upscale African-Americans for white-bread suburbanites, is that the Johnsons start their journey in a highly dysfunctional state rather than ending up that way after a week on the road. It's a potentially interesting twist, but the sibling screenwriting team of Todd R. Jones and Earl Richey Jones' choppy, sloppy script doesn't credibly convey the evolving family dynamic it's aiming for. Though the writers have a sound TV track record (``The Hughleys,'' ``In Living Color''), it appears that they neglected to pack good comic sense for their first jaunt on the big screen Interstate.

What we get instead is a lot of frantic burlesque, tepid clashes of cultural sensibilities and as much toilet humor as a family-targeted ``outrageous'' comedy can get away with. Too often, gags are set up, played halfway through, then forgotten. And the ones that eventually pay off tend to be so ridiculous, they strain the believability of this cartoonish enterprise.

Cedric plays Nate Johnson, a successful Southern California insurance professional. It's time to head back to Missouri for his massive extended family's reunion, where Nate hopes to finally wrest the nuclear Family of the Year award away from his competitive older brother Mack (an overdoing-it Steve Harvey).

Trouble is, to win Johnson Family of the Year, you have to have a family. Unbeknownst to the folks back East, Nate's wife Dorothy (Vanessa Williams) moved down the block six months ago after her husband proved unsupportive of her career goals. She's agreed to go to the reunion, but the marriage is dead in all but name only. And it isn't the best couples' therapy to be cooped up together in a tricked-out, Burberry-patterned Lincoln Navigator (the dealer screwed up, to conservative Nate's chagrin; ain't that a scream?).

Especially with their three crazy kids - teen sexpot Nikki (Solange Knowles, who gets off a good line at big sister Beyonce's expense), aspiring rapper D.J. (Bow Wow, feloniously mugging through every scene) and adorable, fantasizing little Destiny (``Hughleys' '' Gabby Soleil) - horsing around in back.

As happens in these things, the Johnsons encounter purportedly funny stereotypes as they make their way across the Great Southwest: insulted Indians, hot-tubbing large ladies, a hot hitchhiker with alarming interests, a crazed trucker, a ticked-off cop. Bad things happen to the Navigator. Degrading things happen to Nate. An incredible song-and-dance number comes out of nowhere - incredible because it's so good and there hasn't been a hint beforehand that anyone's rehearsed it for a second.

None of which means that ``Johnson Family Vacation,'' which is lackadaisically directed by music video and TV commercial veteran Christopher Erskin, is any dopier than the Lampoon ``Vacations.'' But the Chase films had a cheap ironic tone that made the silliness more palatable than Johnson's sincerity, which just seems to emphasize the flaws in the formula. That, and the fact that this movie's comedy runs strictly on fumes, makes the whole effort seem like a waste of resources.

Bob Strauss, [phone]

bob.strauss(at)dailynews.com

JOHNSON FAMILY VACATION - One and one half stars

(PG-13: bathroom humor)

Starring: Cedric the Entertainer, Vanessa Williams, Bow Wow, Solange Knowles, Steve Harvey, Shannon Elizabeth.

Director: Christopher Erskin.

Running time: 1 hr. 36 min.

Playing: Wide release.

In a nutshell: Strained, lackadaisical comedy about a road trip to a family reunion wastes Cedric the Entertainer's formidable humor skills.