The following map shows US 311 and other relevant routes as they existed just prior to the changes that were implemented in 1934:
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:
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:
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:
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:
US 311 is no longer directionless, and it is no longer intra-state. But it should still be decommissioned, for a few reasons: