Ideally, a roadway should be continuous with junctions only appearing when other roads or ramps intersect. Unfortunately, when the original Tiger maps were loaded, junctions were placed at every location where two roads appeared to cross. Since an overpass may 'appear' to intersect with a freeway from a two dimensional view a lot of unneeded junctions were added to the map. Generally unnecessary junctions are not harmful, but they are better to be removed if truly unnecessary.
Are any two-segment junctions ever necessary?
Sometimes there are reasons for junctions with only two segments. These include:
- Loop roads. A single segment cannot loop back upon itself, so a junction is required to create two separate segments. It does not matter where the junction is located, so long as each segment meets the minimum segment length. Some roads have two separate segments that share the same start and end junctions creating two alternate paths between them. These configurations cause routing problems and require one of the two segments to have a 2-segment junction. More details are covered in Junction Style Guide on Loops.
- Ramp or freeway splits. There are cases where a freeway may split into two separate freeways. In order to provide navigation to drivers, it may be necessary to create short segments on the freeway to show the two different road names at the split. Under certain situations it may be best to make the segments as short as possible, so long as each segment meets the minimum segment length. This is covered in detail in the Junction Style Guide.
- Long segments. Segments are best kept under a certain distance. See the article segment length for more information.
- Segment Property Change. When a segment property changes between intersections, a two-segment junction may be required:
- Road, city, or state name change. When the road, city, or state name changes between intersections, add a junction so the segments on either side may have a different name.
- Elevation Change. When elevation changes at complex interchanges, a junction can be added to introduce an elevation change.
- Speed Limit Change. When the speed limit changes between intersections, add a junction so the segments on either side may have a different speed limit.
Removal justification
If any of the above criteria are present, do not remove the junction. Otherwise, the two-segment junction is unnecessary and can be removed.
Identification on the map
The two ends of a segment are highlighted when it is selected in WME. If each end of that segment does not have at least two other segments connecting to the end, it may be an unnecessary junction. Be sure to review the criteria above before removing it.
Removal best practices
After reviewing the criteria above to be sure the junction is not necessary, when you select the junction in question, if you see the trash can icon in the upper right corner then you can click the trash can to remove the junction. Two other less advisable methods are bridging the segments and dragging them together.
If the trash can icon does not appear, it means the junction separates two segments that are not identical. Possibly the road, city, or state name is different. It also may indicate one of the connected segments are locked above your editing rank. Last, the segments may have different routing directions, so check them to be sure they are set correctly.