May 7, 2009: I-70 between I-270 and I-25. Notice the “Colo Spgs” in the background BGS for I-25. Also notice the wide numeral for US 6.
US 85 has an independent route until it gets south of Denver and then disappears until the Texas state line. The tiny segment in El Paso, less than 10 independent miles, isn’t worth the ambiguity. Either truncate it at Castle Rock and let the piece into Mexico get a different number, or get Colorado and New Mexico to sign the concurrent segments. (Colorado is notoriously bad at this. US 40 vanishes into the ether for many miles at a time.)