?Johnson Family Vacation? could be the lost sequel to the ?National Lampoon?s Vacation? series. And it should have remained lost.

Packing all the tired trappings of the raunchy road-trip genre, this loutish comedy plays out as a loosely threaded collection of shrill jokes and clich?d sight gags.

All the predictable highway hijinks are clumsily tossed in: The crazy hitchhiker, the run-in with the traffic cop, the mishap with a construction crew, the encounter with a mad trucker.

In his first starring role, Cedric the Entertainer melds well enough from brazen, outrageous fringe character to average-guy lead player.

But the choppy direction by first-time director Christopher Erskin and lame script from rookie sibling screenwriters Earl Richey Jones and Todd R. Jones never allow Cedric to do much more than play uptig ht patriarch.

The supporting cast likewise is stuck in one-dimensional roles: Vanessa Williams as stern wife and mom, singers Solange Knowles and Bow Wow as bratty teens and Steve Harvey as an obnoxious oaf of a brother.

Chevy Chase?s original ?Vacation? flick mined the wafer-thin premise of the family road trip with some clever gags and misadventures that resonated with anyone who ever spent too much time stuck in a cramped car with people they know too well.

?Johnson Family Vacation? is nothing but bad schtick as Cedric and his big-screen loved ones travel from California to an annual family reunion in Missouri.

Cedric plays Nate Johnson, recently separated from wife Dorothy (Williams), whom he persuades to tag along and play at happy home life so he can challenge his overbearing brother (Harvey) for the clan?s family-of-the-year trophy.

In tow are the Johnsons? foxy daughter (Knowles), rapper-in-training son (Bow Wow) and youngest daughter (Gabby Soleil), who?s around mainly for a few feeble bits about an imaginary dog she carts along.

They squabble, they clash, and just like your own family, they quickly get on your nerves.

Nonsensically dropped into the mix, then just as strangely yanked out, is Shannon Elizabeth as a wacko hitchhiker the Johnsons pick up.

Harvey takes the prize for most grating performance as Nate?s older sibling, the reigning family-of-the-year champ. Long before the inane competition begins for the family trophy, Harvey has overstayed his welcome.

Cedric, also a producer for the movie, doubles as Nate?s grizzled, incomprehensible uncle for a few moments of meagre, repetitive humour.

?Johnson Family Vacation,? a Fox Searchlight release, is rated PG-13 for some sexual references, crude humour and brief drug material. Running time: 97 minutes.