Interstate Highway relations

Directionality

Main article: Route directions

Most, but not all of these highways should be divided into separate ways (dual carriageways) for each direction by now. At the moment, there are two different approaches for indicating which direction a particular way goes. Although it may look hard, it is actually relatively simple to convert from one to the other using JOSM and the relation analyzer. Right now, there is no consensus on which method is better, and mappers should not change the approach used for a completed relation.

• One relation for each direction of the highway.
  • Simplifies relation analysis and speeds up editing and browsing.
  • For example, one direction would contain only northbound ways, while the other would contain only southbound ways. Example: I 5 north I 5 north.

• One relation for both directions of the highway.
  • Simplifies creation and verification of relations.
  • Relation analyzer supports this now, but slightly more processor-intensive on the analysis server.
  • Enter a "role" for each constituent way. Potlatch provides a small textbox on the same row as the relation for entering roles.

In both cases, the role of each member way should correspond to the carriageway's signposted direction (i.e., north for a northbound set of lanes). Nothing else should be used for the role (unless there are multiple roadways, such as express and local, or upper and lower). Do not tag ways themselves with a "role" tag! Example: I 71 north; US 52 east I 71 north; US 52 east.

State Lines / Administrative Boundaries

Interstate Highway relations should be on a state-by-state basis, e.g. I-90 in MA, I-90 in NY, I-90 in PA, and so forth. A rule of thumb would be if the milestone number resets, start a new relation. Tie all state relations together with a SuperRelation for the interstate.

Avoid relation proliferation, if possible; if a suitable relation already exists for your state on the route you are tagging, you can reuse the existing relation in your area. In Potlatch, do a relation search on the existing relation's number.

Additional Tags

Interstate relation tags refer to the entire stretch of interstate they cover. See Interstate Highways for advice on tagging physical details (speed limit, etc...) of the ways themselves.

0x

1x

2x

3x

4x

5x

6x

7x

8x

9x

Hawaii

Alaska

Puerto Rico