In his follow-up to the mega-hit (and slightly overrated) “The Hangover,” director Todd Phillips pairs that film’s breakout star, Zach Galifianakis, with Robert Downey Jr. in a “Planes, Trains and Automobiles” redux about two strangers forced to travel across the country together.

The comparisons to that previous road movie are inescapable. What matters here is Galifianakis and Downey’s solid comic timing, especially through the film’s more implausible moments. It’s more of the same weirdo antics from Galifianakis (a good or bad thing depending on the outlook), and Downey basically plays a meaner but still charismatic version of his “Iron Man” persona.

The movie gets predictably sappy in the final act, but not enough to completely dismiss the R-rated crass that comes before it. “Due Date” isn’t a great comedy, but it contains enough of what counts: Laughs.

Grade: B