TN 385 currently has an interchange with I-40. As such, in theory, the sections of TN 385 directly connected to I-40 could be signed as an interstate today. However, the new interstate is destined to be a 3di, I-269. I-269's 2di parent, I-69, probably will not have an interchange with I-269 at either location for another 20 years or so: (1) an underlying assumption of TDOT's Lamar Corridor Study has been that Mississippi's section of I-269 will be completed around 2030 and (2) the new terrain section of I-69 from I-40 to TN 385 has been divided into four construction segments, which in conjunction with tight money, might mean completion by 2030 could be overly optimistic (TDOT's description of four segments as follows:
The segment 9 from Hernando, Mississippi to State Route 385 in Tennessee will follow along the existing alignment for I-55 to I-240 then to I-40. Then from I-40 the alignment will follow a new alignment west of State Route 51 to State Route 385 (Future I-269). The new alignment has been divided into four different projects as follows:
1. From I-40 to South of State Route 388
2. From South of State Route 388 to Fite Road
3. From Fite Road to North of Woodstock/Cuba Road
4. From North of Woodstock/Cuba Road to State Route 385 (Future I-269)).
(
http://www.tdot.state.tn.us/i69/segment9/status.htm)
Non roadgeeks probably would not care that the 3di child would not be connected to its 2di parent for such a long time. Businesses probably would want I-269 signage ASAP. Would AASHTO have objections to a 3di not being connected to its 2di parent for such a long period of time?
My primary question is: What should be the triggering event for I-269 signage to go up around Memphis?
My secondary question is: Should I-269 signage installation be done in conjunction with initial I-69 signage through Memphis, including possibly designating US 51 parallel to the new terrain section of I-69 described above as "TEMP I-69"?