Sixteen trucking and delivery companies filed for bankruptcy in less than a month. Some ran one truck. Others operated fleets with dozens of drivers. Diesel has climbed above $6.50 a gallon, on top of insurance, maintenance and other costs. The filings don’t show that fuel alone caused these bankruptcies, but they show how little room some carriers have left when expenses rise. If you run a truck, what’s putting the most pressure on your business right now?