The Guide to Understanding the Highway Numbering System, Part 2 November 6, 2017

This article provides a guide to the numbering system for the United States Numbered Highway system which is often called the U.S. Highways, Federal Highways, or U.S. Routes. Part 1 of the Guide to Understanding the Highway Numbering System covered the Interstate Highway numbering system. It will also help you to understand the geographic layout of the U.S. Highway system.
The U.S. Highway routes are the precursors to the Interstate Highway system that was created in the 1950’s. These routes vary from two-lane undivided roads all the way to the Interstate-class limited-access, divided freeways. These highways are marked with a white shield against a black background.

Two-Digit Routes
The U.S. Highways are numbered in a particular system with the two-digit odd-numbered routes generally running from north to south and the two-digit even-numbered routes running from east to west. The pattern for the numbering system also begins with the lowest numbered odd routes starting on the east coast and going to the highest numbered routes on the west coast. For example, U.S. Highway 1 extends from Fort Kent, Maine to Key West, Florida on the east coast. U.S. Highway 101, which incidentally is considered a two-digit route, extends from Port Angeles, Washington to Los Angeles on the west coast. U.S. 2 runs from Houlton, Maine to Bonners Ferry, Idaho across the northern United States. U.S. 98 runs from Bartow, Florida to across the southern U.S. The U.S. Highway system numbering system, which increases from east to west and north to south, is the reverse of Interstate system to minimize confusion in the numbering system.
Initially, the highways that ended in zero or one were considered the main routes and many of these extended from one coast to the other or from the northern boundaries of the country to the southern boundaries. With the advent of the Interstate system, which often parallels the U.S. Highways, many of the U.S. Highway routes have been truncated, decommissioned, or extended to the point that they may not adhere to the original layouts when the system was initially established. For example, the legendary Route 66 has been decommissioned and replaced by the Interstate Highway network.

Three Digit Routes
Three digit numbered routes are spurs of the parent routes and may branch off from the parent or run near the parent. For example, U.S. 231 begins as a spur of U.S. 31 and runs generally near U.S. 31 from St. John, Indiana near Gary to Panama City, Florida. Some of these may not follow the original pattern of the highway system due to the changes over the years and the altering of the two-digit numbered routes. The first digit of the three-digit route increases along the parent route to follow the east-west and north-south numbering system. For example, U.S. 111 in Maryland, U.S. 211 in Virginia, U.S. 311 in North Carolina, and U.S. 411 in Tennessee, which are spur routes of the parent route U.S. 11, are numbered higher as they go from east to west.

Bannered Routes
Bannered routes are auxiliary highways that are loops, spurs, or alternate routes and have a banner above or below their number on the signage to designate the route. Common banners are ALT (Alternate), BUS (Business), BYP (Bypass), and TRUCK.

Divided Routes
Divided routes are that are evenly split routes and use the designation of E (east), W (west), N (north), or S (south) to designate the alternate routes. This is not the same as divided highways which refer to the dividing of the lanes on a specific route. For example, U.S. 9W is a split route between Fort Lee, NJ and Albany, NY. These divided routes are becoming less common as new designations are not being approved and older ones are being eliminated.
As noted earlier, there are exceptions to these rules and as additional interstate highways are built, it will make it more difficult to conform to the numbering system as available numbers to fit the pattern become limited.
This article should help with your basic understanding of the U.S. Highway system and helps to contrast the difference between the U.S. and the Interstate Highway systems. For information on the Interstate Highway system, make sure to read my article entitled The Guide to Understanding the Highway Numbering System, Part 1.

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