Here’s an overpass query that folks can use to search for potentially missing route relations.
[out:json][timeout:2500];
way[highway][name~"State Highway"]({{bbox}})->.highways;
.highways < ->.routed_highways;
rel(bw.highways) -> .parent_routes;
way(r.parent_routes) -> .routed_highways;
(
.highways;
- .routed_highways;
);
(._;>;);
out skel qt;