For whatever reason around Rochester, NY it's showring NY 47 (hasn't existed in decades) and has some random pieces of road with other numbers that don't exist there (like NY 35).
It only renders the data that's in the map. If the data is wrong, you can leave a note on OpenStreetMap.org about it.
I'm not seeing those numbers on regular OSM, so I'm not sure where they're coming from.
Well, to explain it, some renderers use the ref= tag on roads to determine what its route numbers are. The "new and improved" way to do it is to use a relation, which is a way of grouping multiple nodes or ways, and applying tags to all of them. The OSM-Americana style exclusively uses relations for figuring out the route number/network of a route, rather than using the ref key. I've done some searching and can't seem to find the relation causing it though, but there appears to have been a redaction done a few months ago from someone copying other maps... so that could be the culprit, someone copying old maps into OSM... and it has since been removed? Anyways, the live demo uses maptiler which uses a cached copy of the map data rather than the most recent map. If it was indeed removed from the map we'll see it in the next maptiler update.
Edit: Someone found it! It was deleted 25 days ago. The change will make its way to maptiler eventually.
https://www.openstreetmap.org/relation/12234370/historyIt would be great if there’s a map legend of some sort.
I’m not sure what’s the difference between bright solid red and hollow red or dark black and hollow black.
There are also roads that turn from solid black to bright red and there’s really no difference in grade between the two segments.
Alright, so this may require a bit of backstory. OSM uses the british classification system for roads: motorway, trunk, primary, secondary, tertiary, unclassified, and residential. All of these demonstrate the importance of a road except for "motorway" which is strictly based on road quality.
At some point in OSM history, US mappers decided to use trunk as a tag for what Paul Johnson would call "proto motorways". Basically any divided 4 lane highway regardless of speed or access control. This is an issue because trunk is meant to be the most important non-motorway roads (if you take the same general idea of the british classification system and try to translate it over). Trunks are a legal classification in the UK, while in the US the road network is a lot more messy.
Recently mappers got together across the US and slowly state by state decided trunk should be for important long distance connections. So, for example, an ideal state network looking like Mississippi's does. The network of Motorways and Trunk Roads showing the most important city to city routes in a state's network on zoom level 7.

Those roads you're seeing that are dotted or go back and forth between black and the light red are likely in states that haven't or refused changing their definition of trunk to fit this importance classification. Oklahoma and Arkansas for example.
