LA CROSSE, Wis. (AP) — The state transportation secretary says Wisconsin's transportation system is facing a shrinking revenue stream. Mark Gottlieb says the department faces a $600 million funding gap in the next two-year budget cycle. He says fuel tax revenues are projected to decline 20 percent over the next decade due to Americans driving fewer miles in more efficient vehicles. The tax is the DOT's single largest source of funding. The Legislature hasn't approved an increase for the fuel tax since 1997, and the 30.9 cent tax hasn't been adjusted for inflation since 2006. He says the goal of the meetings is to get feedback on transportation needs and their financing.