Todd Phillips has defined himself as a director of “male buddy” comedies. With a string of successes including “Old School,” “Starsky & Hutch” and last year’s summer blockbuster “The Hangover,” Phillips ends 2010 with “Due Date,” a wild comedy with more compelling characters and an arguably deeper story than his past films.

Peter Highman (Robert Downey Jr.) is one flight away from being with his wife as she gives birth to their first child. But Ethan Tremblay (Zach Galifianakis) gets them both on the no-fly list after Ethan disregards airline protocol. Without his wallet and ID, which were left on the plane, Peter has no choice but to join Ethan on a conventional Hollywood duo road trip to get home in time.

Phillips uses his proven style of comedy well with a group of men in over-the-top situations as they scramble desperately toward their goal. Galifianakis embraces an awkward character similar to his character in “The Hangover” with his dry execution of ridiculous lines. Downey’s character has a darker comedy, which works well considering the character is empathetic. But lowball humor, such as when Peter has to endure Ethan’s awkward sleeping habits spending a night in the car, doesn’t add much to the film except cheap laughs.

With two famous and experienced leads, the protagonists generate a substantial story about life’s journeys. Galifianakis’ character is comically oblivious, but he steps up his performance as he carries the emotional weight of a scared individual making his way in the world. Downey plays a perfect antithesis to Ethan. Peter is initially an uptight jerk who takes advantage of Ethan and is prone to anger. One scene involves Peter’s not-so-socially-acceptable way of dealing with an annoying kid. Not only is it surprisingly laugh-out-loud funny, but it also enhances the story by calling into question Peter’s ability to be a parent.

Like most of Phillips’ movies, a little suspension of disbelief is needed to enjoy the mayhem, such as a car chase that is somewhat unbelievable because of how much destruction it causes. Some of the jokes also seem too childish, such as when one character runs into a car door.

“Due Date” is enjoyable on many levels, both as a comedy and a compelling story. It is one road trip people can definitely hop on board with.

“Due Date” was written by Adam Sztykiel and Alan R. Cohen and directed by Todd Phillips.