TV REVIEWS : DON’T LOSE ANY SLEEP OVER ‘CRUISIN’ ’

The saving grace of “Keep on Cruisin’,” the late-night series that CBS is introducing tonight, is that it has the honesty to admit the obvious.

“Every late-night show owes a great deal to David Letterman,” a comedian named Sinbad, who co-hosts the low-budget variety show with singer Stephen Bishop, says midway through the premiere (11:30 p.m., Channels 2 and 8). “The man has come up with so many great ideas, it’s just hard to find something to top it.”

So “Keep on Cruisin’ ” imitates it. And, in doing so, proves anew--as Jay Leno did with his late-night special on NBC last November--that Letterman’s silliness and TV put-downs aren’t nearly as easy to pull off as he makes them look.

To be taped at outdoor locations around Los Angeles--”because we can’t afford a studio,” Sinbad says--”Keep on Cruisin’ ” demonstrates how hard it is trying to be hip and flip by setting the first edition at a tire store on Sunset Boulevard in Hollywood. The straining for laughs continues from there, though there are two pleasant musical interludes from Billy Vera & the Beaters.

“Keep on Cruisin’ ” isn’t worth missing any snoozin’.

Meanwhile, back by no one’s demand tonight is “Charles in Charge,” a new version of the short-lived 1984 series on CBS in which Scott Baio played a college student who was caretaker to three children of a working couple. The show wasn’t good enough to stay on the air then and it hasn’t gotten better with age.

The only thing that’s changed in the syndicated edition, which debuts at 7:30 p.m. on KTLA Channel 5 and hereafter will be seen Mondays at 7:30 p.m., is that Charles is working for a different family. Instead of two boys and a girl, he’s now in charge of two teen-age girls and an 11-year-old boy.

They’re in the same house, though, as tonight’s show explains. While Charles is on a camping trip, his former employers move out and sublet the home to a new family, who of course agree to take him with it, sight unseen.

It makes as much sense as anything else in this series.

But if the first show is merely forced and unfunny, the second, on Monday, additionally is crass with its archaic, lugheaded jokes about abstract art and sniggering attitude about nude modeling--including leers from the 11-year-old.

Worse, both episodes use the younger children as foils to thwart Charles’ apparently endless quest for sexual adventure, giving rise to the question, “Who’s in charge?”