quote:Originally posted by Robearjr
Interstates are also supposed to to terminate at another interestate.
There's no such rule. The terminous of lots of interstates is not another interstate. I-66 ends in Washington, DC, I-40 ends in Wilmington, NC, I-81 ends at the Canadian Border (as do many interstates), I-10 ends in Santa Monica, I-90 ends in East Boston., I-78 ends at the Holland Tunnel, I-80 ends at Rt. 101 in city of San Francisco, etc, etc.
I think what you are confusing is the designation of the prefix number of an auxillary Interstate. Auxillary interstates with an even number should connect to an interstate (or auxillary interstate) on either end, while an auxillary interstate with an odd number only connects to an interstate at one end.
The auxillary routes with an even number do not need to connect to the same interstate at both ends. For example, I-476 (the Northeast Expressway in NE Pennsylvania), spurs from I-76, but the other end connects to I-81 in Scranton, Pa. Another example is I-690 in Syracuse NY which spurs from I-90 on the west side of syracuse and runs parallel to I-90 until ending at I-481, another auxillary interstate on the east side of Syracuse.
There are , of course, roads that break these rules. Actually, there's always at least one road that breaks the "rules" of number designation. For example, I-82 is fully north of I-84 and I-39 lies fully east of I-45 and I-49 but west of I-43.
Other oddities on the interstate system includes some roads with wrong way concurrency, such as the nine mile stretch near stretch Wytheville, VA, where one can be traveling on both I-81 North and I-77 South at the same time, and in the other direction, on I-81 South and I-77 North at the same time.