I will update the E58(A1) waypoint name to E58.
As for bypasses, its complicated, like many things Japanese. Almost every expressway and many urban national highways in Japan are built from a set of connected "bypasses". A new section of road usually has its own bypass name. They actually use the katakana version of the word "Bypass". What we would consider a bypass in the US will also have bypass in its name. I spend a lot of time trying to figure out what the bypass name of a road segment is because most online info uses the bypass name and not the national highway designation.
I've done about 60% of the national highways so far, and have identified four types of road segments.
1) The current road (the main line). Originally the national highways went right through towns, but over time bypasses have been built to widen the road or avoid town centers and other obstacles, and the current road moved to the bypasses.
2) Old roads. When the original route is replaced by a bypass, usually the old route is transferred to the prefecture or city and given a local designation. (This transfer may take several years, so new bypasses are often associated with "temporary" old road sections.) But in some cases, the original route retains it national highway designation, so there are two routes with the same designation.
3) Bypasses. These are built usually to avoid town centers or other areas of heavy traffic. They are not old roads and they are not the current road. They often connect at both ends with the current road or another national highway. I believe "Byp" is the correct banner for these roads.
4) Spurs and connectors. They connect the current road, old road, or a bypass to another road, often an expressway.
There is some degree of ambiguity. Sometimes its tough to determine which is the current road and which is the bypass, or which is the current road and which is the old road. True bypasses and spurs are usually pretty obvious.
Japan does not sign its bypasses, old roads, or spurs any differently than it does current roads - they all get the blue rice ball sign with a number on it. Sometimes an overhead sign will indicate which route is the bypass, or the old road, but this is not prevalent.
There are also national highway bypass designations on many expressways, typically those that are free and were built with prefectural money. These bypasses usually do not have national highway signage because in general, Japan does not multi-sign concurrencies.
