As you will know from Oil 101, natural gas has been finding an increased use as an alternative to oil as a transportation fuel in a particular niche: natural gas is particularly suited to urban bus and trucking fleets as vehicles can be refuelled at the same spot each day and the distances vehicles can travel on a single refuelling is slightly more limited than with diesel.
Until relatively recently compressed natural gas (CNG) had been used mostly for buses and other urban people carriers. Now that natural gas fundamentals have changed such that natural gas prices are extremely low relative to oil, it makes not just environmental sense, but has also become economically sound for private businesses to convert.
An interesting and well researched story today by Brian Baskin at Dow Jones describes how most beer in New York City is being, or will shortly be, delivered with natural gas powered trucks rather than diesel.