Illinois trucking companies are thrilled to start paying a 100 percent increase in the state's gas tax. Why? It swaps a fee that supported the state’s overall finances for a tax that ultimately benefits the industry’s bottom line. The $45 billion capital plan passed by the General Assembly doubles the gas tax from 19 cents to 38 cents a gallon—the first hike in nearly three decades—and ties it to inflation. The rate for drivers of diesel-powered commercial trucks rises even higher, to 45.5 cents a gallon. The plan pays for infrastructure improvements like roads, bridges and transit systems.