One issue, of course, is that for some people, the fastest drivers, the left-lane becomes their de facto lane, and they may force out dozens of drivers (necessitating all kinds of disruptive lane changes) for their own benefit. This raises another possibility. The road could be grooved in such a way, as in Japan’s Melody Road (that’s an engineer inspecting the road pictured above) to produce a certain sound at a certain speed. Grooving could presumably be laid so that drivers going over a certain speed produced a really grating, revulsive sound (music might be tricky as one person’s annoyance would be another’s delight). In a sort of Nudge-like way, drivers could choose to stay in the unpleasant lane if they wished, but they would be subtly steered toward the more harmonic travel lanes.
A video of Melody Road is below. (Unless you speak Japanese, you’re only going to hear the sweet sound of asphalt)