Map of the Western Beltway, including exits, toll locations and available plazas and rest areas. Select an exit, travel plaza, toll plaza or other location from the map, or use the location list to get information and a close-up map of that location, plus any nearby gas stations. Serving Montana with Pride. Our Mission: MDT's mission is to plan, build, operate, and maintain a safe and resilient transportation infrastructure to move Montana forward. Our Vision: To accomplish this mission, MDT will set the gold standard for a highly effective, innovative, and people-centric department of transportation. Core Values: Eight core values guide all MDT employee behavior. Description. This map layer is a combination of street maps from county government street centerlines, USGS 1:24,000 roads, and the Census Bureau TIGER 1:100,000 roads. We are currently acquiring the remaining county government roads of the more rural and northwestern counties.