Amid the nation's shale gas boom, natural gas is being considered as an alternative to diesel to fuel heavy trucks. The "Blueprint for a Clean and Secure Energy Future" unveiled by U.S. President Barack Obama last week calls for "putting in place new incentives" for medium- and heavy-duty trucks that run on natural gas or other alternative fuels and providing a credit for 50 percent of the incremental cost of a dedicated alternative-fuel truck for a 5-year period. "The natural gas vehicle market is already growing but the vehicle incentives the president calls for would help accelerate that growth and...