TRYING TO TRAVEL INCOGNITO: Tammy (Melissa McCarthy, right) and her grandmother Pearl (Susan Sarandon), set out on a road trip to Niagara Falls after Tammy’s life falls apart when she loses her car, job, and catches her husband sleeping with the next door neighbor. Since Tammy has no money and car, Pearl agrees to pay for the trip so she can escape from her retirement community, which she feels is like a prison for senior citizens.

After winning an Emmy for her TV sitcom Mike & Molly in 2011 and receiving an Oscar nomination for Bridesmaids in 2012, Melissa McCarthy apparently was able to write her own ticket when negotiating with the studios. She used that leverage to create a production where she would not only portray the title character, Tammy, but also make her screenplay debut.

Keeping it all in the family, Melissa had the studio hire her husband, Ben Falcone, to direct and co-write the film, which might not have been a problem if it weren’t his first time attempting either of those tasks. The upshot is that their ill-advised collaboration has produced a road comedy that has precious few laughs.

And in the process, the picture squandered the talents of an impressive cast that included Academy Award winners Susan Sarandon (Dead Man Walking) and Kathy Bates (Misery); Oscar nominees Toni Collette (The Sixth Sense) and Dan Aykroyd (Driving Miss Daisy); and veteran actors Allison Janney, Sandrah Oh, and Gary Cole. Unfortunately, the talented cast was given a cringe-inducing script that is more crass than funny.

As the film unfolds, we find Tammy having one of those days. First, when a deer darts in front of her car, she totals her Toyota Corolla on her way to a thankless job at a fast-food restaurant. Then, she’s fired by her exasperated boss (Falcone) for arriving late for the umpteenth time. On her way out the door, she launches into an expletive-laced tirade during which she trashes the premises in front of the mortified staff and customers.

Things go from bad to worse when Tammy arrives home earlier than usual and catches her husband (Nat Faxon) in bed with their next-door-neighbor (Toni Collette). Shocked and brokenhearted, she decides to take a break from her mess of a life, only to realize she can’t even afford to leave town because she has no cash and no car.

Her grandmother, Pearl (Sarandon), agrees to subsidize Tammy’s vacation provided she can tag along for the ride, since her retirement community feels like a prison for old people. The two set out for Niagara Falls and raise a ruckus at every port-of-call along the way, whether jet skiing, over-imbibing, trading insults, picking up strangers at bars and diners, triggering pyrotechnic displays, landing in jail, or crashing an all-lesbian barbecue on the 4th of July.

If only some of their sophomoric antics were witty or amusing. The film is a depraved escapade that will disappoint even diehard Melissa McCarthy fans.

Fair (*). Rated R for profanity and sexual references. Running time: 96 minutes. Distributor: Warner Brothers.