With no CGI or big-name stars to suck you in, indie movies often have to fall back on the virtues of a decent script and a well-chosen soundtrack. Matthew Bissonnette’s low-key comedy drama, Passenger Side, rides into town trailing some rather dubious “poster quotes” in its wake. I’m talking about the so-called reviewer who claims “No, it’s not like Sideways; it’s a lot better in fact”.

See what he did there? The bracketing of this movie with Alexander Payne’s 2004 comedy, suggests that Passenger Side is nothing short of a modern classic. After all, Sideways picked up the Oscar for best adapted screenplay, which even allowing for the stupidity of the Academy’s voters still means something. But in my opinion, this likeable story of a couple of LA slackers on the road to nowhere, isn’t in the same league as any of writer/director Payne’s best work.

Matthew Bissonnette’s third full-length film stars his brother Joel as Tobey, the ex-junkie brother of failed novelist and world-class cynic Michael (played by Adam Scott). The movie begins with Michael in his Echo Park bachelor pad, trying to dodge a call from Joel, who needs a ride somewhere. Reluctantly he agrees to take his younger sibling to some “job interviews”, but the real purpose of their day-long car trip turns out to be a case of “cherchez la femme”. Joel is desperate to locate Theresa (Robin Tunney), supposedly the love of his life, but the trail involves many diversions and misadventures.

Shot on HD video in just 14 days, Passenger Side also has a pleasingly retro feel about it. There’s Mike’s car, a 1975 BMW that remains a defiantly iPod-free zone. Mike has invested in a brand new cassette deck but has no cell phone — there will be no texting and definitely no “sexting” here. Instead, this movie features the rare sight of a character getting out of his car to use a public pay phone. What’s most old-fashioned, of course, is the reliance on dialogue to drive what little plot there is. If you imagine that two guys driving round LA County promises pedal-to-the-metal scenes and frenetic action, think again.

As in Sideways and the more recent Easier with Practice, it’s the wildly differing attitudes of the protagonists that create dramatic interest. In short, it helps if one guy is a loner and a misanthrope and the other more of a “glass half full” type. Mike, whose stock in trade is words, rarely says anything that isn’t laced with several layers of sarcasm. Tobey, though he’s obviously led a rather dissolute life, claims to be at a turning point now that he’s joined the Scientologists. But as the brothers try to reconnect over their shared history, writer Bissonnette’s message seems to be that it’s Mike who needs to wake up to his failings.

The bulk of Passenger Side‘s 85-minute running time is taken up with the kind of bizarre incidents that you expect to see in road-trip comedies. Perhaps the critic who compared this with the work of Judd Apatow was referring to Mike’s close encounter with a transsexual prostitute; a stop-off at an adult movie set; or the bleeding Mexican who’s chopped off a couple of digits. Bissonnette stops short of giving these incidents the full gross-out treatment because there’s a genuine humanity about his characters. Earlier in the film, the brothers bicker over the significance of “different strokes for different folks”, but when Tobey criticises Mike for living in LA and not knowing any Spanish his point is well made.

Although Passenger Side is smartly scripted and both leads convincingly inhabit their characters, it all feels a little aimless. The mystery element concerning Michael’s fruitless phone calls to a (possible) girlfriend is kept largely in the background until the film’s rather hurried conclusion. When we do finally get to meet Tobey’s beloved Theresa, she only has one underwritten scene in which to explain her behaviour.

Matthew Bissonnette obviously laboured long and hard over honing his dialogue, choosing the locations and selecting music from the likes of Leonard Cohen, Wilco and Silver Jews. But the lack of structure in his story robs it of any real emotional impact and the non-stop sarcasm becomes a little wearing by the end. If Miles from Sideways were comparing this movie to a wine, I’m afraid it would be a Merlot rather than the much-prized Pinot Noir.

(Passenger Side is released in UK cinemas on 1 April.)