Variations in road exposure and traffic volumes in the United States in areas susceptible to landslides

There have been many efforts in the United States (U.S.) to identify landslide threats for specific roads, but we are unaware of any effort to examine the entire national road system. We use geospatial tools to estimate the lengths and percentages of total length of roads in landslide-susceptible areas and differentiate results by road type, jurisdiction, and susceptibility level. We summarize traffic-volume counts in landslide-susceptible areas in terms of annual and maximum hourly counts using geospatial zones based on the concept of stopping-sight distances. A substantial percentage of the U.S. road network is in areas with some level of landslide susceptibility from 35% (by length) of all roads to 68% of county routes. Several Interstate highways have considerable lengths of road in areas with highest landslide susceptibility. There are hundreds of sites with high hourly and annual traffic volumes in areas of highest landslide susceptibility, indicating potential threats to life safety and traffic disruption.