Tim, you’re right to be skeptical about DART’s sudden about-face on the bus deal. To me it’s all about a win-win for Mayor Tom Terrific: If and when he does run for higher office, his green bona fides (as per this arrangement) will be beyond reproach; plus, it won’t hurt for Leppert to have ‘ol deep-pockets Boone in his corner. While I guess it makes sense to support compressed natural gas when the Barnett Shale’s in your backyard, should that be the deciding factor? Besides diesel’s advantage on bus cost, the executive director of the Maryland-based Diesel Technology Forum points out that there’s an “infinitesimal” difference between clean diesel and natural gas in terms of air pollution. Allen Schaeffer also notes the big-time “retrofitting” costs for natural-gas bus systems, and says that 80 percent of new-bus orders nationally are going the clean-diesel route. Then he adds this kicker: Transit decisions in favor of natural gas are inevitably “influenced by ‘deals’ arranged with the gas suppliers … when in many cases the economics are not favorable” for the natural-gas option. Could that have anything to do with DART’s new fuzzy math?