For Southern California's clean air and public health advocates, it must have felt as though their ability to clear skies of harmful air pollution in the nation's smoggiest air basin had suddenly disappeared in a cloud of diesel soot.
When it was passed earlier this month, the state's landmark legislation to hike vehicle fuel taxes to raise billions of dollars to repair and improve California freeways, roads, bridges and other transportation facilities included wording limiting the ability of regulators to crack down on big-rig trucks, Southern California's greatest source of smog-forming emissions.