Cool project! The OSM vehicle interpolation along way geometries is a nice touch. If you want to push further into realistic vehicle routing — where vehicles actually navigate junctions and follow shortest paths — Moveet (https://github.com/ivannovazzi/moveet) might be a useful reference. It's an open-source fleet simulator I built that runs A* pathfinding on GeoJSON/OSM road graphs and streams positions over WebSocket in real time, which could complement your existing layer setup.