Maine is nearly 100 percent dependent on petroleum to fuel rail, truck, bus, aerospace, marine, and automobile transportation vehicles. Transportation accounts for more than half of the State’s energy use, emissions, and costs. Transportation is responsible for 54 percent of Maine’s annual greenhouse gas emissions. When emissions are analyzed by vehicle type, 59 percent of Maine’s transportation-related emissions are from light-duty passenger cars and trucks; 27 percent are from medium- and heavy-duty trucks; and the remaining 14 percent come from rail, marine, aviation, and utility equipment vehicles. The proposed rule is the first step to reduce carbon pollution from medium- and heavy-duty trucks in Maine, and an additional step to reductions in ozone, fine particulate matter (PM2.5), and toxic diesel particulate matter. To avoid missing compliance years and delaying the rule’s benefits, it is imperative that Maine adopt the ACT rule as soon as possible.