Many fuels have been proposed as alternatives to gasoline. Most face the early adopter with same problem -- where to refuel while on the road? A tool to address this chicken and egg dilemma has been created by the National Renewable Energy Laboratories, an Internet atlas showing the location of hydrogen, compressed natural gas, and other fuels.
The Google-map based map tracks sources for liquefied natural gas, propane, hydrogen, electric, compressed natural gas, E85, and biodiesel.
Looking at the results, I was immediately struck by the ease with which a vehicle running on compressed natural gas could cross the country on I-94 through the northern tier, where stations are evenly dispersed along the route.
Travelers along I-90, which parallels 94 to the south, would not be so fortunate. There are no CNG refueling stations listed along that route for many hundreds of miles through the corn belt.
The same site shows which areas of the country have a high density of vehicles running on alternate fuels. Hybrid electrics are most common in the L.A. area, San Francisco, Chicago, Boston and New York. You're unlikely to encounter one in the northern plains states.
Much more data about alternative fuel use can be found at the Alternative Fuels and Advanced Vehicles Data Center.
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