Rt. 5? Do you mean I-5? I'm curious if using "Rt." instead of "I-" is a regional thing. Where are you located? Typically Rt. would only be used for a small state road, not a major interstate highway.
Actually, in the Boston area, it's "Route 128." Despite it never being indicated as such at exits or on maps.
You have omitted the rather important qualifier “Southern” from your description, as that usage is a key differentiator between Northern and Southern California.
— https://www.kcbx.org/post/how-you-refer-us-101-says-lot-abou...
I moved to Northern California (Santa Clara County) in the late 80s and I still use the same monikers. If I take a trip to Big Sur, I tell folks I am going to take the 17 to PCH and drive down. Old habits die hard.
https://www.kcet.org/shows/lost-la/the-5-the-101-the-405-why...