Of the 4.1 million miles of federal and state highways in the U.S., 2.2 million miles (or 54%) are unpaved, gravel roads. In the Pacific Northwest and Alaska, unpaved gravel roads provide critical transportation access, with some communities relying on just a single highway for access into and out of town. In such cases, these highways become a critical component of the infrastructure, and there is a need to ensure that safe access is always available to the communities. To maintain a high level of access, the following data regarding these unpaved, gravel roads must be collected: (1) geometric alignment, (2) width, including shoulders, (3) condition of the unpaved surface, (4) impact from unusual highway loads, (5) impact from geo-hazards, (6) susceptibility to flood events, and (7) influence of adverse weather conditions. This study plans to use the Idaho highway database to identify unpaved, gravel roads in Idaho that are critical for access to rural communities. Once identified, information regarding their existing condition (items 1 to 3, above) will be used to assess their vulnerability other impacts (items 4 to 7, above). Much of this initial evaluation will rely on information that is readily available in the database. To complete the first phase of the proposed project, we plan to perform a pilot study of a couple unpaved, gravel highways using field data. The procedures developed for this comprehensive evaluation will provide guidelines for evaluating the remaining critical routes, which should provide a valuable database of these critical assets. The investigators will use the data generated from this project to develop a comprehensive gravel roads rating system on a five years’ plan.