Nitpick: US 101's terminal point shouldn't be CA 60 but I-5 southeast of Euclid Avenue, as there's a US 101 only half-interchange with Euclid, labeled as 1 on OSM (GMSV shows no exit number on the final overhead, nor any gore exit assembly). This might require an adjustment on I-5's .wpt? I'm not sure this plays well with the one-point-per-interchange rule in this instance.
That would be in line with
one of neroute2's suggestions (made long ago, when I was deferring most changes to non-usaca routes not needed to get usaca finalized) that US 101 be extended southeast to the merge with I-5 near Lorena St. But he also pointed out that US 101's mile 0 seemed to be north of the CA 60 interchange, approximately where 101 passes under westbound I-10 (with no connection with 101), and 101's interchange with 7th St. That would mean truncating, rather than extending, US 101. It is also more consistent with Caltrans' online exit list for US 101, which has the 7th St. interchange as 101's southernmost exit, as well as the online Postmile Query Tool, which treats the 101 roadway south of 7th St. as part of route 5 rather than route 101. Also, the 7th St. interchange happens to be US 101's legislative south end, though that language doesn't necessarily preclude Caltrans from fudging the endpoint a little.
This is a messy and confusing situation. Given conflicting information, I would split the difference between the "extend" and "truncate" options and just leave the US 101 route file mostly as is, with 101 ending at CA 60. ("Mostly" in order (a) tweak 101's I-5/10 point, or at least its label, given the lack of an actual direct connection to I-10, and also (b) relabel adjacent US 101 waypoints, some of which are in use.)
