Calculate distance from polygon to nearest existing line in geometric network, along network routes

Question

In ArcMap 10.6, I have a parcels layer and a sewage lines geometric network for a small town. Many of the parcels are still undeveloped. In an effort to accurately assess them for tax purposes, their distance to existing "main" lines affects their value (further from main line = less valuable since connecting parcel to main lines costs a lot).

I need to find distance for each parcel to nearest existing main line along geometric network. In attached image, I need to calculate the distance following the path of the blue line, which follows the route along future mains until it hits existing main. I know that if I did a spatial join of parcels to nearest existing line, it would do so like the red dashed line, which is not what I want.

Is there any way for me to find these distances?

Answer 1

This is solved with Network Analyst Tools, and specifically Find Closest Facilities

You must build a network dataset using your "proposed" layer. Assuming it's a simple sewage network, you probably don't have to set detailed parameters like turns, cul de sacs etc (like in a road network). And the only cost should be Length, which is by default.

In Find Closest Facilities, the Facilities will be the "Existing" layer and the incidents will be the "Parcels" layer. The network dataset will be the one you created. This will find the network distance (along the network, not euclidean) from the incidents to the closest facility.

Pay attention as to what exactly you set as Facilities. Can you connect to existing network on any place, or only on vertices? In case of the latter, you should convert your Existing layer to vertices and use them as your Facility layer.