In 1980 Arkansas, Missouri, and Tennessee jointly requested the specific designation
US 412 for a route across the three states. After
initially balking at the number "412" at their June 1980 meeting, AASHTO approved the proposal later that same year (at their Nov. meeting). So the questions are:
- How did those states arrive at the number "412"?
- Why did AASHTO approve it, after initially rejecting it?
That was discussed a bit in
this thread, where in post #168 Mike asked the question, "Was that the lowest number that didn't conflict with state route numbers in any of those three states?" (After all, it's generally desirable if state DOTs don't have to renumber existing routes when a conflicting US route number is approved for their state.) So I recently spent a little time investigating that possibility, and here is what I've found so far:
- In 1980, TN seems to have been still working through their 1xx numbers.
- It appears most 2xx and 3xx weren't used until 1983 or later.
- 400 wasn't used until 1986; 416 was 1987-88 (and there have been no 4xx state route numbers in between those).
- So in 1980 TN wouldn't have had any reason to leapfrog straight to the 4xx range.
- MO didn't have any 4xx numbers at the time (and even now has only a couple).
- In 1980 AR was getting close to using up all of its 3xx numbers.
- 392 and below were commissioned in the 1960s.
- 393 and above were commissioned in the 1970s.
- Not many 4xx numbers are in use even now, and the few that exist appear to have been designated in the 1980s.
- So it seems pretty clear that AR was the only state that would have had a reason to propose a 4xx number.
- But the reason for the specific number "412" is still unclear.
However, it's only a matter of time before someone uncovers a historic document that explains the rationale. My hope is that this thread will be used for posting that discovery.
Meanwhile, this post provides some necessary background for understanding
the likely reason for US 425's number, which is discussed in
this thread.
