Checked out the unsigned portion of CA 710/I-710 south of the I-210/CA 134 interchange this week:
https://flic.kr/s/aHBqjzCKVc
What's amazing about this is that they have exit numbers as if the entire freeway would've been completed.
CalTrans likes to lay out mile numbers and postmile numbers as if all proposed roads will eventually be completed, however unlikely that is.
For example, I-80's first exit in San Francisco, Seventh Street, is exit 1, as you'd expect. But its postmile number is 3.91. That reflects I-80s formerly planned west end at CA Highway 1, 19th Avenue.
Shouldn't that Seventh St exit then be exit 3? I'm pretty certain exit numbers were supposed to reflect postmiles.
I-80 has been legislatively defined to end at US 101 (Bayshore and Central Freeways) since 1965 or so, after the Western Freeway (from Golden Gate Park to the former Fell Street interchange complex off the Central Freeway) was vociferously opposed during the San Francisco freeway revolts.
Prior to the 1989 earthquake, the section of I-80 coming off the Bay Bridge westbound was signed as "I-80 / US 101" (possible holdover from when 80 was defined along the east-west part of the Central Freeway and then to the canceled Western) but is now primarily signed as "US 101 SOUTH - San Jose", another of those CalTrans "implied TO" situations.
This is different from the other scenarios in which exit number and postmile may conflict:
- I mentioned I-380 above, with its exit number range from 5 to 7. The route definition still includes the likely-to-never-be-built portion from Pacifica at Route 1 to I-280. (I still think the route should be extended as a short 2-lane road to Skyline Boulevard/Route 35, but that is probably never happening).
- Route 14 is legislatively defined to start at Route 1 near Malibu (passing through Reseda) but that extension southwest of Sylmar has been dead for at least 5 decades; the exit numbers for what has been built explicitly begin at I-5/Golden State Freeway.