Bus route relation OSM tags available in bicycle edge costing?

Hi, I'm working in a fork where I'm playing around with tweaking the logic for bicycle costing. One of the things I'd like to try out is to see whether it's possible to penalize directed edges that are part of a busway (whether via built-in costing, or via a dynamic costing input). It appears that in NYC, when OSM ways overlap with a bus route, that bus route is expressed as a relation containing that way — and I'm [taking this note](https://github.com/valhalla/valhalla/blob/master/lua/graph.lua#L2180-L2184) to mean that relation -> way tags post-processing may not squarely exist.

If I wanted to try to poke around at this, is there any precedent for post-processing relation-bound way information like this? I wasn't able to find where that shielding/highway info lives currently (I'm new to C++!), and am not sure if this is the right way to think about exposing relation information in the context of bicyclecost.cc. I've thus far had success with querying other salient features (weighting the oneway-ed-ness of a street, for example) in bicycle costing, so am hopeful about this idea as well. Thanks for any pointers you can share about how these types of OSM tags might be expected to work in a Valhalla context!