I have begun a second pass through the Japanese national highways, starting with the N300-N325 group.
As a result of the second pass, and doing recent updates because of new road openings, I've decided that I should change the way I designate the main road. Before, when there was a choice I followed the oldest existing route, typically the route through a congested urban area. The other option I designated as a bypass. I now believe I should put the main road on the through route, which is almost always the bypass.
Additionally I am removing the Byp designation from routes. There is no official designation marking a route as a Bypass, and routes are not signed as Bypass. I formerly based Byp on the route location and function. (An added complication is that almost all new road segments have their own unique name that contains Bypass, so everything new is a bypass in some way. Ambiguity is the norm in Japan and in Japanese.)
I now plan to use this route naming scheme:
1) The main road is the through road when there is a choice. The route name is Nxxx.
2) All other routes with the same number have an appended location abbreviation - e.g. N300Yam, N300Mat
3) No routes will use Byp in jpnh.cvs.
Some expressways are also designated as "motorway on general national highway". I will treat the concurrent national highway designation the same as any other route and not mark them as Byp.
