We all dream of winning the lottery, but for Woody Grant the dream has become a conviction.

A septuagenarian who spends most of the time in his own little world, he believes that the marketing flyer with his name on it represents a real reward. And since he lost his driving licence a long time ago, the old fella decides to walk across two states to collect the money.

Tired of having to pluck his deluded dad from the highway, Woody's youngest son, David, decides to drive him the 750 miles from Montana to the lottery office in Nebraska. And so the fool's errand hits the road.

Alexander Payne specialises in modest, relatable human stories, told with minimum fuss and maximum truth, often involving men with challenging relationships to their families. His last, The Descendents, featured George Clooney as an Hawaiian estate agent struggling to be more than a "back-up dad" to his daughters, while his wife lay in a coma; About Schmidt had Jack Nicholson's painfully introverted retiree setting off in a Winnebago to attend his estranged daughter's wedding.

Like About Schmidt, Nebraska is a road movie - Payne's favourite genre and one that showcases his feel for the American landscape as well as the country's eccentric, small-town characters, of whom Bruce Dern's Woody may well be the oddest of all.

Woody's drink problem will lead to a cracked head, lost dentures and a detour to his Montana hometown, where his family and community are all too eager to believe his assertions of wealth. In particular, Woody's old business partner and his nephews - a redneck Tweedledum and Tweedledee - circle like vultures for a slice of the pie.

His immediate family do their best to look after him. The only thing that David (Will Forte) hopes to get out of the journey for himself is a few days with his father; his good nature and adaptability guides the journey - in other words, the film - on its course. He is lent amusing support by his brother Ross (Bob Odenkirk, Saul Goodman in Breaking Bad) and their mother Kate (June Squibb), the film's glorious joker, who seems at first to be no more than a nag but reveals herself to be a strong, ribald and loving dame.

It's a measure of Dern's skill that such a quiet, even blank performance can hold centre stage. With his unkempt beard and wisps of white hair over a liver-spotted pate, a hip that's probably artificial, and a mind that shuts down for minutes on end, it's fair to say that physically and temperamentally Woody is a mess. He doesn't apologise for his drinking, or his failings as a parent. But the longer he spends in his childhood home, the more we learn about him, and the greater our understanding of how, once, he might have been an appealing figure.

Can it be coincidence that Payne has turned to both Nicholson and Dern for leading roles? The pair came to prominence in the 1970s, one of the richest periods in Hollywood's history (memorably co-starring in The King Of Marvin Gardens) and both became known for larger-than-life characters. Payne has encouraged them to turn down the volume, eliciting great, late-career performances from both.

There is a sort of 1970s hue to the whole of Nebraska, actually, in its casual pacing and black-and-white, cinemascope photography. With a gallows humour and enormous charm, the result is a small, beautiful reflection on family life, growing old with dignity, and how children can help their parents carry a modicum of hope into old age.