Relation editing in Potlatch 2
Create a new relation in Potlatch 2
It's a good idea first to look at a similar relation. (Most interstates or primary highways are part of a relation, and many bus routes are relations.) Click on a segment of the relation to highlight it. Click on the "Advanced" tab at the bottom of the tag window. At the bottom of the Advanced window is the Relation section. Doubleclick on the name of the relation. A window will open called "Edit Relation." Scroll to the bottom of that window and click on "Advanced."
You will see a list of tags. Please look at them carefully. The editor does not suggest tags, and they all have to be typed in by hand. It is a good idea to take notes on the tags listed there.
For most roads the tags will include "network," "ref," "type" and "route." The "network" for a state highway in the United States, say Arizona, will be "US:AZ." The "ref" will be just the number of the highway because the state already has been specified. The "type" of relation would be a "route" (as opposed to related areas, such as sections of national forest). And the "route" is a "road."
Once you are familiar with the proper tags for the type of relation you are trying to create, close the Edit Relation window. You are back at the Advanced tag window. Go to the Relation section toward the bottom and doubleclick in the white space in the Relation column. A window called "Select Relation" appears. It may offer a list of relations that already have been created. (Note that a road may be part of more than one relation, and one of those relations may be a bike or bus route.) If those choices are not appropriate or you are creating an entirely new route, click on the "New Relation" button at the bottom of the Select Relation window.
The Edit Relation window appears again, but this time there are no tags. It is blank. That's why it is important to look at an existing relation first. Click on the "Advanced" tab at the bottom. A window appears that looks much like the Advanced tags window. There is an "Add" button toward the bottom. Click on it to add each tag. Hopefully, you will have made notes so you have the correct tags. When you are done, close the Edit Relation window. You will see the new relation at the bottom of the Advanced tags window.
Add members to a relation in Potlatch 2
Find an existing member (preferably one that is a member only of that relation). Then click on the new member. Then shift-click on the button at the bottom right with the two intersecting circles that look like a piece of chain (this copies the relation memberships from the previously selected way or node to the currently selected way or node). It also copies the role, which you may need to change. You also can pick the relation from the list of relations in the Select Relation window if one applies. You also can select from a list of nearby relations, but that is unwieldy if there are a lot of nearby relations. Video example