Google 'Alps balcony roads'.
Yeah, that is what I was imagining. Do cars drive on those balcony roads? They look like they're made for bicycles.
Perhaps the Piaggio Ape?
I'd have to think that building a 300 or 400 mile long trail in Oregon could cost on the order of $200+ Million. If it was made from Vancouver BC down to San Diego, it would be big bucks.
I'm not sure one could ever recover the capital costs through tolls, but what would be "reasonable" for through cyclists (say > 50 miles)? $20 per cyclist + $10 for each additional cyclist in a group)? $5 for < 16? Add more tolls for ferries (although give a discount for cyclists with the through passes).
Apply cheaper rates for short distance cyclists, pedestrians, etc, or even free. Annual passes for locals.
That would put one in line with a national park, maybe.
In fact, one could make an argument that one could build a 1000+ mile long national park..
I.E. bring in some federal bux.
I'm not sure one could recover the capital costs, but perhaps pay a chunk of the annual maintenance.