Infrastructure would be my first response. There has not been an investment in infrastructure in North America—in Canada and the U.S., and in Mexico, to a degree—that would make it as easy to fill up at the corner station as you can now with your conventional gasoline-driven internal combustion engine.
The cost advantage and the supply advantages that you're talking about are also relatively new. As recently as five years ago, we did not have 100 years' worth of natural gas supply, but new technology has been created that allows for access to natural gas that was not economically accessible in the past. That has helped to drive the price down.
It's a combination of those factors that makes the equation you create very viable and perhaps will help motivate the shift. It certainly is in the work we're doing with the return-to-base and corridor vehicles.