Defense Access Roads Improvement Act This bill updates provisions and requirements related to the Defense Access Roads Program, which authorizes the Department of Defense (DOD) to pay for construction and maintenance of defense access roads. DOD must establish a formal mechanism under which a state, county, or municipality may petition to certify roads as defense access roads, and DOD must respond in writing. Additionally, DOD must maintain and regularly update on a federal website a list of all defense access roads that includes certain unclassified information about each road (e.g., the military installation that is closest to the road). The bill also includes military installations and commercial shipyards as sites that utilize defense access roads, thereby authorizing the use of program funds for the maintenance or construction of such roads. Further, the bill requires that defense access road projects abide by certain wage and materials requirements.