But what I want to do is highlight specific lines one at a time. For instance, only highlight the Asakusa Line. I can do that in Google Maps, but what I want to know is if I can specifically do it using the Google Maps API.
Moreover, how would you highlight heavy rail/overland lines like the Yamanote Line? The TransitLayer only works on subway lines.
I have been able to extract route relations for specific railway lines in OpenStreetMap (using JOSM), but Google Maps is a lot more confusing.