Wyoming/highway classification

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This is a proposal for standardized road classifications in Wyoming as part of a larger discussion about classification standards nationwide (United States/Highway classification). You're free to add on and edit the contents of this page.

This is a centralized page for rural Wyoming highway and other road classification.


We use several different metrics to evaluate the importance of every highway. These include, but are not limited to:

  • Traffic counts
  • Road quality for motor vehicles (e.g. number of lanes, average speeds, pavement)
  • Number and quality of alternate routes available
  • Whether the roads connect any populated locations of note or serve popular recreation areas

We do not copy any of the governmental ways of classifying highways (functional class, US vs state vs county route, etc.), but we do use them as guides to help with the particulars.


WYDOT Sources

Other Sources


Trunk routes

Corridor Endpoints Reason
WY 89/US 89 I-80 to US 26 Best route to Jackson from Salt Lake City and other points to the south. Crosses into UT at one point (and briefly ID), but the route is primarily located in WY. It's technically faster to use a combo of I-15, US 30, ID 34, and WY 239 rather than the souther portion of this route, but the WY 239 portion is in such poor condition that I can't consider it the best route.
US 30 ID to I-80 Route to Pocatello and Idaho Falls from points to the east and southeast, including Rock Springs and Cheyenne.
US 191 I-80 to US 26 Route to Jackson from anywhere to the southeast, including cities like Denver and Cheyenne.
US 26 ID to I-25 The second-most-important east/west route across the state after I-80. The part west of Jackson is part of the route to Jackson from anywhere to the west or south. The part between Jackson and Casper forms a long corridor with significant traffic where almost no other roads exist, and also serves as part of the route between Casper and Idaho Falls.
WY 28/WY 789/WY 120 US 191 to MT This route doesn't connect any large population centers (unless you count Billings to Rock Springs, or Riverton as a large center), but serves as the most important north/south route in a large and remote area of the country. Without this, I-25 would be the only north-south route tagged trunk in northern Wyoming, leaving nothing in the 300 miles between it and Idaho. I debated keeping the trunk tag on WY 789 the whole way instead of taking the WY 120 detour, but the WY 120 route is quicker both time-wise and distance-wise, goes through Cody (the most important town in the area), and has roughly equal traffic.
US 287/WY 220/WY 257 I-80 to I-25 The route to Casper from any place to the southwest, including Salt Lake City.
US 287 CO to I-80 The fastest/best route to Denver from points to the northwest.
US 26 I-25 to NE The route to Scottsbluff from the northwest.
WY 59 I-25 to I-90 The route between Gillette and Cheyenne.
WY 259/WY 387 I-25 to WY 59 Probably the best route between Gillette and Casper. Gets a decent amount of traffic and the road is good-enough quality that I'd say this is a better route (and certainly faster) than taking I-25 east to WY 59. But I'd welcome opinions from others more familiar with the area.
US 18 I-25 to SD Part of the route between Rapid City and Denver. It's faster to use US 85 the whole way south of Lusk, but traffic count data shows that more traffic seems to take US 18/20 to I-25 rather than staying on US 85.