Can I do this in configuration of my profile instead of updating the GH code? I use the GH map matching as a gradle dependency in my application:
implementation 'com.graphhopper:graphhopper-map-matching:8.0'
You could use a profile based on the vehicle: roads, but this way you won’t be able to distinguish raceways from other types of roads that are normally not accessible for the car profile, so modifying the code is probably your better choice. But you might be able to use the unmodified jar and only inject your modified parsers using GraphHopper#setTagParserFactory.
It worked in the end to create extended versions of these two parsers, extended VehicleParsers class and a new TagParserFactory, inject into the Graphopper instance for the 8.0 version at least. Looks like there is changes to this structure in trunk though.