Despite the fact it's the quickest way to get from Birmingham to Croydon, there's a larger dramatic reason behind Locke taking the M6 and the M1 motorways down south. Locke's commute isn't happening at an especially inhospitable, in-the-wee-small-hours time it's late evening (presumably in the autumn/winter) and he's supposed to be going home to watch football, which usually kicks off around eight o'clock. As such, there's still plenty of cars about on the road, but not enough to create too much of a jam like rush hour would and he's in an unremarkable car (fair play, it's a BMW, but still) surrounded by other unremarkable cars, all trying to get somewhere. The setting points out that no matter what Locke's travails and how important they seem, he's nothing more than one among many, and everyone else could be in a similar situation just two lanes to the right of him. Sure, Locke's business problem is a bit bigger than most if the build and planning goes balls-up, the firm could lose millions but the themes of work pressures and family troubles are probably being played out in cars all over that motorway, even if Locke's problems are far more acute and pressing at that point. It's another tip-of-the-cap to the sheer unremarkable-ness of it all, and that, ironically, is what makes it remarkable.