Here are some categories that interest me:
Longest stretch of highway across a single county: in Texas, I-10 across Pecos County, 100 miles
Longest highway entirely in one county: in Texas, SH 54 in Culberson County, 55 miles
Longest stretch of highway between two consecutive highway intersections: in Texas, SH 118 between US 67/90 and FM 170, 78 miles
Longest stretch of Interstate between two consecutive Interstate intersections (in one state): in Texas, I-20 between I-10 and I-30, 421 miles
Longest stretch of Interstate between two consecutive Interstate intersections regardless of state lines: Anyone?