Melissa McCarthy is back with “Tammy,” one of her strongest roles yet -- a result of her direct creative control on this project -- but apart from her performance, this road-trip comedy unfortunately coasts by on autopilot.

Co-written and directed by McCarthy’s real-life husband, Ben Falcone and produced by Will Ferrell, Murphy’s Law is in full effect for Tammy. On her way to work she hits a deer and totals her car, making her late to work which results in her termination. Bruised and dejected she returns home to find her husband having an affair. So Tammy flips the bird to the world and skips town for the first time in her life, bringing her boozing, neglectful grandmother Pearl (Susan Sarandon) along for the ride.

Tammy and Pearl’s joy ride turns into a comedic therapy session as they both unload their problems on each other; Tammy’s false sense of security is pitted against Pearl’s alcoholism and as they both cope with each other they come to find a mutual understanding and common ground. And certainly casting Sarandon immediately opens comparisons to “Thelma and Louise.” Tammy and Pearl definitely find their fair share of trouble, minus the famous cliff, as they chase boys (Mark Duplass and Gary Cole) and in turn are chased by the law.

McCarthy’s Tammy is a further exploration of her comedic brand. She is like the modern equivalent of John Candy, though with an added spike of coarseness. One moment she is affable to the point of adorable then unleashes torrents of profanity and rage. She has perfected this brand so well that by now the impact is rather muted. McCarthy shows a stronger range as Tammy than any previous performance; there is something so appealing about a sad clown and McCarthy again does a fine job showing jilted Tammy’s despair behind her frequent childish outbursts.

McCarthy’s script with Falcone is undeniably filled with heart and there’s a palpable connection between her and Sarandon. While the age discrepancy takes some getting used to – Sarandon is grandma, Allison Janney plays daughter and McCarthy is granddaughter –McCarthy and Sarandon are an unexpectedly enjoyable team. McCarthy softens Sarandon’s edge and Sarandon gives some dramatic substance for McCarthy to flex her diverse acting chops.

However, while road trip movies offer plenty of comedic material, “Tammy’s” pit stops are just all-too familiar. There is hardly anything new here we haven’t seen before and the typical road trip plot devices pop up like clockwork. Though, the script does have a few prized gems of dialogue, which are primarily reserved for Tammy.

For the past decade, women in comedy have been given a more prominent platform. Indie comedies, especially, are a haven for female-centric stories, but major Hollywood players are still trying to catch up. Like her contemporaries Tina Fey and Kristen Wiig, Melissa McCarthy once again helps level the comedy field with a high-profile film primarily featuring a nearly all-female cast. Check it: Toni Collette, Kathy Bates, Allison Janney, Sandra Oh, Gary Cole, Mark Duplass and Dan Akyroyd.

Now with that cast, “Tammy” should be a homerun, but sadly, apart from McCarthy and Sarandon’s dynamic duo, there is an abundance of wasted talent as the entire supporting cast is given very little to do. Overall, “Tammy” doesn’t break any new ground but it certainly doesn’t harm the road trip genre it calls home.

Warner Bros. Picture. MPAA Rating: R. Running time: 1 hour and 36 minutes.