Quick thoughts on representing a road network in JSON. Basically TopoJSON for OSM nodes/ways.

example.json

{
 "type": "network",
 "nodes": [
   {"coordinates": [-71.13568, 42.38196], "properties": {}},
   {"coordinates": [-71.13555, 42.382523], "properties": {"highway": "traffic_signals"}},
   {"coordinates": [-71.134087, 42.38384], "properties": {"railway": "level_crossing"}},
   {"coordinates": [-71.141007, 42.386862], "properties": {"highway": "crossing"}}
 ],
 "geometries": [
   {"type": "LineString", "nodes": [0, 1, 2], "properties": {"highway": "primary", "name": "Main Street"}},
   {"type": "LineString", "nodes": [2, 3], "properties": {"highway": "motorway_link"}}
 ]
}

It's not much different from just GeoJSON with points and lines, but finding intersections would be an explicit integer (or maybe some ID) comparison rather than doing the floating point match on the coordinates. And modifications to any coordinates update all references.