I drove VA I-77 recently between I-81 and the North Carolina state line, and was wondering... why is the entire 32 mile portion only posted at 65 mph? When VDOT raised the speed limit on rural interstates back in 2010, virtually every segment of interstate outside major cities was increased to 70 mph.
This included
- The entirety of I-81 (except over Christiansburg Mountain, Roanoke, Staunton, Harrisonburg, and Strasburg)
- The entirety of I-64 west of Williamsburg (except through Richmond, Charlottesville, over Afton Mountain, and near Covington / Clifton Forge)
- The entirety of I-66 west of Gainesville
- The entirety of I-77 north of I-81 (except through the two tunnels)
- The entirety of I-85 south of Petersburg
- The entirety of I-95 south of Fredericksburg (except through Richmond-Petersburg)
VDOT originally kept I-64 between Charlottesville and Afton Mountain posted at 65 mph, along with I-81 near Winchester posted at 60 mph, though within a few years after 2010, raised both areas up to 70 mph.
The one that stands out though, is the 32-mile segment of I-77 south of I-81. MM 1 through MM 8 can be justified for 65 mph due to the mountain pass over Fancy Gap, but the segment from MM 0 to MM 1, and MM 8 through MM 32 is no different than any other rural segments of I-81, I-64, or I-77 north of I-81 posted at 70 mph. It features two independent roadway sections separated by a large median, has some gentle grades, and can safely handle 70 mph. One could argue there are a few advisory curves signed for 60 mph, however, my counter-argument to that would be similar 60 mph advisory curves on portions of I-81 north of Roanoke, I-77 north of I-81, and I-64 west of Lexington, that exist on segments posted at 70 mph.
Given VDOT posted virtually all of I-81 outside the urban areas at 70 mph, including on those windy 60 mph curve portions, what is their justification for keeping I-77 at 65 mph? From what I saw driving it, most traffic was flowing around 77-80 mph, roughly the same speeds traffic was moving on I-81 just north of there, which is posted at 70 mph. As soon as one enters North Carolina, the speed limit increases to 70 mph.
I'm just curious to as if there's an engineering justification as to why VDOT omitted all of I-77 south of I-81 for any 70 mph increase. It's not any different design-wise than other highways they raised, with the exception of Fancy Gap which is justifiable to keep 65 mph. It is not located near any major cities or population centers, all of the interchanges have low traffic volumes and no major traffic generators (with the exception of the US-58 interchange). The roadway cross-section is consistent with other rural interstates in the region (for example, I-81).