That well-trampled terrain known as the Hollywood Hills get another unnecessary workout tonight in the premiere of "David Cassidy - Man Undercover," the NBC cop show at 10 on Channel 4. Camaroc careen, tires squeal bloody murder, an U-turns are U-turned willy-nilly. Even if we hadn't seen all this before, it would hardly qualify as the week's top treat.

Cop shows came under fire during all the flak about violence on television, and most of those subsequently outfitted with cement shoesies are not missed. To add a new one at this stage, even as a vehicle for Cassidy's comeback seems an inherently but pointlessly risky notion.

Cassidy's doleful doe countenance may be harmless and semi-personable enough, but the program essentially just devides th emoody old "Mod Squad" by three and turns it into a solo. Cassidy plays an undercover cop riddled with guilt over the fellow youngsters he has to bust. He's vaguely anti-establishment and given to spells of dread and brooding.

It isn't angst, actually. It's angstypoo.

On the opener, our hero infiltrates the cleanest-talking gang of hot-rodders in the world in order to break up a supermarket-robbing ring. Unfortunately the program makes the thieves - at least the two played by Brian Kerwin (as "Ernie") and Brad Reardon (as "rick") - more attractive and sympathetic than the doubt-striken cop played by Cassidy. Eventually it's time for him to say, "Give it up, Ernie: it's all over," but not before several routine car chases around familiar twisting roads. "Man Undercover" really boils down to "Good punk, bad punk" and you don't much care which punks win.