The problem with a "demand redistribution" type scheme, of which variable road pricing would be an example, is that it implicitly assumes people are there during peak hours for the sheer hell of it. What you'd find if you actually asked people who drove regularly (as opposed to attempting a top-down planning exercise carried out mostly by people who spend most of their lives within London lounging about in the back of chauffeur-piloted Jags) is that the gridlock itself acts as a suitable deterrent... which would be why you tend to find the most problematic congestion at times when people simply have to travel; for example, I'd love to breeze into work at about 10-11 o'clock when all I'll encounter is a brace of vans, a bus or two and maybe an octagenarian bumping their way to the supermarket in a Micra on the way there, but my employer and clients certainly wouldn't be having any of that.
As a practical demonstration, observe what happened when fuel pump prices briefly touched their 122ppl/135ppl peak; bugger all difference to the everyday commuting drag, but the roads were deserted in the evenings - people didn't magically relocate their non-negotiable journeys, they cut out the optional ones so they could still pay for what travel they needed. This of course has an impact on out-of-town businesses, and particularly anything that relies significantly on tourism/passing trade for its income.
Public transport is a nice ideal but for a lot of people it's not feasible; also there's the problem that in the event a route does go somewhere useful, it's already overcrowded before you start thinking about shifting more people onto it from their private transport. Four years of Monopoly money mortgages and fiscal drag on stamp duty hasn't exactly helped, often pricing people out of living within walking or cycling distance of their workplaces.
The solution is reducing the journeys themselves; start seriously pushing home working, video conferencing and other flexible practices where possible, rather than trying to punish people for travel they can't really avoid. It's not feasible in every industry, but there are enough people who travel from a house with a desk, computer and a telephone to an office with a desk, computer and a telephone to make a worthwhile difference. Try getting command-and-control politicians to square that with equally command-and-control management types, though, and you'll find yourself getting about as far and as fast as you usually get trying to make your way past the "temporary" roadworks at 8:30am of a Monday morning...