An action comedy in which the action is rote and the laughs pretty scarce, “Ride Along” is notable only for the accession of Kevin Hart to leading-man status after secondary roles in various ensemble pieces. The motor-mouth comic takes on what’s essentially the loquacious Chris Tucker role from the “Rush Hour” movies, with Ice Cube standing in for Jackie Chan in the laconic straight-man part. It is not a match made in heaven.

It’s made instead in Atlanta, where Cube plays James Payton, one of those hot-shot detectives so familiar from old TV police shows—the sort who drives his captain (here a lieutenant, actually, played in the style of every such character you’ve ever seen by Bruce McGill)) crazy by always going too far and breaking the rules. But of course his unorthodox methods get the job done, violating departmental policy (and indeed the law) but working “on the street.”

Cube essays this role with his customary scowl firmly in place; he seems extremely unhappy whenever he has to crack even the slightest hint of a smile, which he rarely does even when dealing with his partners (John Leguizamo and Bryan Callen)—whom he dismisses as the “brawns” to his brain in their search for an elusive crime lord named Omar—or his beloved sister Angela (Tika Sumpter), whose live-in boyfriend Ben (Hart) he intensely dislikes. A diminutive high school security guard who’s addicted to video games of the hunt-and-shoot variety, Ben strikes James as a wimp unworthy of Angela. And he’s out to prove it when Ben’s accepted to the police academy (hard to believe, given his height). Sensing a chance to humiliate him out of Angela’s life, James invites Ben to ride along with him for a day, intending to use the experience to make the newbie run as far away as he can from the force—and the girl.

This premise might just be enough to serve as the basis for a half-hour sitcom, but over feature length it’s stretched beyond endurance. After several encounters that James sets up to embarrass Ben—a run-in with a bunch of beefy bikers, another with a drunk who’s gone berserk in a mall, a third with a mouthy kid in a park—as well as a slapstick stint at a shooting range, Ben shows his true mettle when, in a turn that’s meant to come as a big surprise, James—and Angela as well—fall into the clutches of the mysterious Omar and his underlings.

The elements involved in that “twist” should shock nobody, since anyone who’s ever seen a movie will spot what’s going to happen well in advance, and the identity of Omar is made obvious simply by scanning the cast list to note which big name hasn’t appeared yet. But they’re all designed to provide Hart with opportunities to riff at length, however implausibly given the situations. And while he’s certainly a funny fellow, a little of him frankly goes a long way; by the close his shtick has grown more than a little stale. The script also panders to a large segment of its audience by positing the ludicrous notion that the innumerable hours Ben’s spent playing a military-style video game has endowed him not only with a detailed understanding of real weapons but a tactical sense that he can employ to outmaneuver guys with automatic rifles and hand grenades. That notion might be comforting to couch potatoes, but it strains credulity even in a piece of formulaic nonsense like this, which embraces every cliché of the genre and improves on none of them.

That’s not simply the result of the script, cobbled together from spare parts (including a drearily extended harangue by the mysterious villain toward the close, along with an obligatory damsel-in-distress sequence) by no fewer than four writers. It’s also to be blamed on director Tim Story, who not only was apparently much too liberal in allowing Hart the chance to run on interminably, but fails to bring much humor to the extended action sequences—a car chase at the start and a couple of big confrontations in the final reel—all of which are messily constructed (Craig Alpert’s editing is at its weakest in them) but—even worse—come across more nasty than nice.

Technically adequate but not much more, “Ride Along” is a ramshackle vehicle that brings Kevin Hart front and center but then strands him with little to work with.