[Tagging] Level crossings on street-running trackage

[Nathan Edgars II]

When a railway runs down the middle of a street (meaning one can drive
on the tracks as long as no train is present), where should a
railway=level_crossing node be placed? At every intersection (other
than those where you are prohibited from turning across the tracks by
turn restrictions)? Only at the ends? At every switch for a
spur/siding (where only one direction of road traffic crosses the
rails)?