There are a few instances where a single short segment may be present between two other segments with no other segments at those junctions. Sometimes these junctions are necessary and should not be removed. 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.