Last time the gas price hit 4 dollars a gallon, people stopped buying SUV's, and started buying hybrids instead. It forced companies like GM to begin work in it's electric hybrid the Volt, and got people to park and take the buses when available.
Of course, gas prices dropped and people being the short-sited people that we are, stopped thinking about fuel prices and started thinking about whatever passing news item they saw in the latest 15 second clips.
Thanks to turmoil in the middle east, we are now witnessing another increase in gas prices, and like last time, bus ridership is up and people are talking about more fuel efficient cars. I can only hope that this time around the high prices are here to stay.