US 311 should have been decommissioned in 1934; why is it still around?

(Latest revision 7-14-2020) 
The following map shows US 311 and other relevant routes as they existed just prior to the changes that were implemented in 1934:

• The green line represents US 220, which was primarily a Pennsylvania route.  On its north, US 220 extended a fraction of a mile into New York, ending in Waverly.  To the south, US 220 passed through the thin panhandle of Maryland and barely entered West Virginia, terminating at New Creek.
• The purple line was US 311.  Its north terminus was at its junction with US 11 in Roanoke, Virginia.  From there it went south into North Carolina, but instead of heading straight through Greensboro, US 311 took a longer route, first heading southwest to Winston-Salem, and then back southeast through High Point.  In other words, US 311 did not follow the shortest route between its own endpoints.
• The thin red line was US 411.  It began in Madison NC and functioned as the most direct route between Roanoke and Greensboro.  South of there, US 411 and US 311 met again and were twinned for about 40 miles before separating at Candor NC.
• The thin blue line through the Virginias had not previously been included as a US route, but in 1934 it was brought into the system as a way to bridge the 200-mile gap between US 220 and US 311.

It was a good plan to connect the two routes, and to unify them with a single number.  But why was US 220 chosen as the designation that would survive the merger?  Either the US 311 or US 411 designation could have been extended north, subsuming the US 220 designation.  In some ways, that would have been a more logical choice:

• US 220 was kind of an inappropriate designation to begin with, as it never intersected its implied "parent" route (US 20).  US 220's number was derived from the fact that it intersected US 120, which could be considered a "sibling" route.  But using that methodology for US route numbering was somewhat unusual.
• Almost all north-south US routes were assigned odd numbers.  US 220 was one of a handful of exceptions, so its number did not fit well when viewed in the context of the entire system. 
• On the other hand, either US 311 or US 411 would have been a good choice for this route. 
• The odd number would have been appropriate for a north-south highway.
• There would have been a junction with the implied "parent" route (US 11) in Roanoke.
• Numbering the route as a branch of US 11 would have also been appropriate because the highway somewhat mimics the curve of US 11 through the Appalachian Mountains.

But instead, the decision made in 1934 was that US 220 would be extended southward, subsuming US 411 and severely truncating US 311.  This map illustrates the arrangement after these changes were implemented:

• The green line represents US 220, which was extended south through the Virginias and all the way to Rockingham NC.
• The purple line shows all that remained of US 311.  South of Randleman, it was overlapped with US 220 only as far as Asheboro, but US 311 was no longer twinned all the way down to Candor.
• The orange line had been the southernmost segment of US 311, but in 1934 it became a segment of an extended US 501.
• The thin red line had also been part of US 311, but in 1934 it was removed from the US route system, instead becoming an NC state route.

What were the reasons that US 220 was extended south (instead of US 311 or US 411 being extended north)?  I can only speculate, but here are a few thoughts:

• At approx. 278 miles, US 220 was the longest of the three routes.  US 311 was about 252 miles, while US 411 was only a little over 100 miles in length.
• US 411 was intra-state in North Carolina, while US 311 ran through two states.  Whereas US 220 was primarily in Pennsylvania, it also had short segments in three other states.  So changing US 220's number would have been a little more complicated, involving coordination between four state highway departments.
• US 411 was possibly already on the chopping block, since it was a short intra-state route.
• US 311 might have been more worthy of consideration if it did not include that strange detour through Winston-Salem and High Point.  This made US 311 an inefficient, somewhat directionless route.

Whether it was for any of those reasons, or perhaps others, officials ultimately decided that US 311 came up short in its matchup against US 220.  

The map above serves to illustrate the fact that, after the US 220 extension and the US 311 truncation, US 311 was pretty useless.  For one thing, US 311 had become a short (~67 mile) intra-state route.  Moreover, despite its diminutive length, most drivers would not have a reason to follow US 311 from end to end, because of its weird 90-degree change of direction in Winston-Salem.  Possibly there would have been some merit in redesignating US 311 as "Alternate US 220" for the benefit of traffic destined for Winston-Salem or High Point.  But the route certainly was no longer worthy of a standalone US route designation.

By 1937 (and possibly before), AASHO had stated, "U. S. routes, less than three hundred miles in length, heretofore established and located wholly in one State, shall be eliminated either by consolidation with other U. S. routes or by reverting to State routes, as rapidly as the State Highway Department and the executive committee of the American Association of State Highway Officials can reach agreement with reference thereto."  Somehow NCDoT never complied with that, and US 311 remained essentially unchanged over the next 70 years.  A few minor alterations were made: the pointless overlap with US 220 between Randleman and Asheboro was removed in 1966, and in the 1980s a freeway (today's I-74) began to be built through US 311's corridor from Winston-Salem through High Point to Randleman.  But none of that changed the fact that US 311 was not worthy of its US route designation.

In 2003, instead of decommissioning US 311, NCDoT petitioned for an extension of the route northeast from Madison to Eden.  AASHTO (which by then had long since stopped concerning itself with the integrity of the US route system) approved their request, even though the extended US 311 would still be an intra-state route.  Since there was no other US route in Eden, this was a perplexing extension, made even more so by the fact that NCDoT did not actually signpost US 311's new segment for another eight years.  But in 2012 things became more clear, as both NC and Virginia requested another extension to the northeast, this time to US 58 in Danville VA.

By about 2014, the entire US 311 freeway between Winston-Salem and Randleman had been redesignated as I-74.  So the US 311 designation in that corridor was redundant, further emphasizing its lack of purpose.  NCDoT acknowledged this in 2018 by asking AASHTO to decommission that segment of US 311.  So this map illustrates the current arrangement:

• The purple line shows the last remaining segment of the original US 311 (Winston-Salem to Madison).
• Other shades of purple indicate the 2003 and 2012 extensions of US 311 (to Eden and Danville, respectively).
• The blue line represents US 360.

US 311 is no longer directionless, and it is no longer intra-state.  But it should still be decommissioned, for a few reasons:

• At only 65 miles in length, US 311 is currently the seventh-shortest US route.  The US route system does not benefit from the addition of routes that short.
  
• With only eight miles in Virginia, US 311 is still essentially an intra-state route.
• US 311 would make a logical extension of US 360, which is already a much longer and more legitimate US route.

Currently US 360 heads southwest into Danville and ends there.  So when NC and VA brought the Eden-Danville corridor into the US route network, that opened up a perfect opportunity to make things right: the US 360 designation could be extended further southwest to Eden, and from there it could continue southwest to Winston-Salem, replacing US 311 all the way to its terminus.  US 360 would then be a respectable 300-mile long route, serving a consistent northeast-to-southwest corridor through two states: