Should it matter how long the highway was signed as a US highway?
I wouldn't think so. I like the idea of being able to grab more esoteric routes like US 122.
Should it matter when the highway was decommissioned? Maybe limit it to those that existed during my lifetime?
In my case, that'd only give me a list of 8 or 9 routes, assuming routes that were decommissioned in their entirety (vice, say, US91). If I were a faster-paced traveler determined to go out and get all these, it may not keep me busy very long.
Limiting the decommissioning date, or lifetime of the route, could make for a smaller more manageable ToDo list. Once it's done, relax the standards, and see where there is to go next.
What routing should I use: the current routing of the route(s) that replaced it,
Not IMO. Changes could be major. Or beyond the scope of what the original US route was (EG NY104). Successor routes will probably be numbered routes clinchable in their own right.
OTOH, this didn't bother me one bit when I followed the Lincoln Highway corridor. I was content to take US30Bus, US30 proper across much of OH, and eventually just I-80 across the west. I clinched
The Route That Eric Took From Portland to San Francisco in 2006 and am mighty pleased with that, and will milk it for all the bragging rights it's worth. No point getting hung up on
regrets.
or the actual path the US highway took immediately before its demise?
That's one possibility. Another is the route it took when it was at its greatest historical length.
Then, there are the routes that had significant relocations at the end, moving from one city to a completely different one.
If you're
really ambitious, you could go for all the old alignments. Every last oxbow. Gotta catch`em all!
Whatever gives the most enjoyment for the person doing the clinching, of course.
