Hi AntBurnett,

The topology join is just that.... we want the culvert to have a durable realtionship with the road way(s).

There are a number of reasons for this... OSM considers the culvert to be part of a waterway, yet in every occasion I am aware of a culvert is an asset that (like bridges) are belonging to Transport Departments (such as DIT, DTP, TMR, Main Roads,  City Services, State Growth as well as LGA's).

Given that culverts are largely considered to be transport infrastructure outside OSM, this topology should ensure that relationships can not only be established but also monitored and called out in particular when using the ID Editor. It should be far more stable than relying on geometry intersection alone.

I hope that carries enough reasoning to stand up :)

Cheers AH