Colorado Highways: Auxiliary Routes

Northbound 8th Avenue at 18th Street in Greeley

This section of my Colorado Highways site is dedicated to what I call "auxiliary routes" in the Colorado highway system. These routes are routes that are full-fledged state highways, but are not marked as such. Instead they are designated as a derivative of another route number. These auxiliary routes include:

• US and State Business Routes: All marked US and SH business routes (BRs) in Colorado are cases where a bypass of the town in question was built, and then the old section of the highway through the town was given the BR designation. However, note that some towns got bypasses built, but the old alignment did not get a BR designation (US 287 in Lafayette, for example).

• Interstate Business Loops and Business Spurs: In Colorado, Interstate business loops (BLs) usually are cases where an Interstate was built that bypassed a town, but the old US Highways through the town got to get the BL designation. In some cases (BL I-70, Limon) the BL is marked as concurrent with these old highways, but in other places (BL I-70, Idaho Springs, which used to be US 6-40) the BL is all by its lonesome self and the US designation was dropped. Also, CDOT utilizes a system of Interstate business spurs (BSs), going from the Interstate into the central part of town, which are not marked at all.

• Spur Connections: These include a myriad of cases. The only thing common to them that they all are very short, and are numbered with the main route's number.

• Other Auxiliary Routes: These routes are ones that don't fit in the categories above: Truck, Old, Bypass, and so on. Some of these routes take the form of non-state maintained, locally designated routes.

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Last updated 1 August 2005

	• US and State Business Routes: All marked US and SH business routes (BRs) in Colorado are cases where a bypass of the town in question was built, and then the old section of the highway through the town was given the BR designation. However, note that some towns got bypasses built, but the old alignment did not get a BR designation (US 287 in Lafayette, for example).
	• Interstate Business Loops and Business Spurs: In Colorado, Interstate business loops (BLs) usually are cases where an Interstate was built that bypassed a town, but the old US Highways through the town got to get the BL designation. In some cases (BL I-70, Limon) the BL is marked as concurrent with these old highways, but in other places (BL I-70, Idaho Springs, which used to be US 6-40) the BL is all by its lonesome self and the US designation was dropped. Also, CDOT utilizes a system of Interstate business spurs (BSs), going from the Interstate into the central part of town, which are not marked at all.
	• Spur Connections: These include a myriad of cases. The only thing common to them that they all are very short, and are numbered with the main route's number.
	• Other Auxiliary Routes: These routes are ones that don't fit in the categories above: Truck, Old, Bypass, and so on. Some of these routes take the form of non-state maintained, locally designated routes.