Rjgambrel/Motorway Islands analysis
This is an attempt to do some analysis of motorway islands in early February 2022 due to a large number of comments just received.
The thought behind this: besides trying to articulate general guidelines it would be good for folks to see some of the actual islands in Minnesota.
This draft attempts to show ALL motorway islands that are in Minnesota. Long lengths of motorways (e.g. cross-state or metro Twin Cities-wide) are not included in this chart. Where an island "touches" the motorway network (consisting of those long sections) it is noted in the chart below.
The chart lists the highway number and an "Island ID". The Island (ID) is the value of a new helper tag called MN_Mway_island. The values are usually <network><ref><suffix>. the suffixes are usually a single letter: a, b, .... Tagging is done only on one of the two carriageways. Usually the west bound or north bound. Suffixes usually start at the East or South of a route. The entirety of each island is so tagged. A turbo query for MN_Mway_island=* in Minnesota will find all tagged ways. (See below a nice query that allows the tags to be visualized directly in overpass turbo.) And of course, instead of an asterisk, a specific Id can be queried such as US169a. (No spaces!) The other columns in the table are:
- Class: whether the highway is a US highway or Minnesota highway.
- sort: allows the table to be sorted in the original order published
- Highway: human readable highway number
- Island ID: the value of the MN_Mway_island tag
- Near: A nearby city in Minnesota
- Int: the number of interchanges. So int=3 means there are 3 grade-separated interchanges in the island section.
- Km: A very rough length of one side of the dual carriageway. This is a guesstimates and could be off by 25% or more.
- MWnet?: whether this island is connected to the larger motorway network of the state
- Notes: additional information to consider
Here is the chart. It is sortable so you can order by any column. Sorting by Highway, Island ID, Int, Km, or MWnet? might be helpful in order to focus on, say the "smallest" or "shortest" islands, or perhaps all the islands on one highway.
| Class | sort | Highway | Island ID | Near | Int | Km | MWnet? | Notes |
|---|---|---|---|---|---|---|---|---|
| US | 2 | US 2 | US2a | Bemidji | 4 | 15 | no | |
| US | 10.1 | US 10 | US10a | Ramsey | 1 | 3 | no | has some RIRO |
| US | 10.2 | US 10 | US10b | Sauk Rapids | 3 | 6 | no | with MN15c a tri-spur island |
| US | 10.3 | US 10 | US10c | Little Falls | 5 | 8 | no | with 371a a tri-spur island |
| US | 10.4 | US 10 | US10d | Perham | 3 | 5 | no | |
| US | 14.1 | US 14 | US14a | Rochester | 1 | 3 | no | edit: neither a spur or part of US52 |
| US | 14.11 | US 14 | US14a2 | Kasson | 1 | 5 | no | |
| US | 14.2 | US 14 | US14b | Dodge Center | 4 | 30 | no | |
| US | 14.3 | US 14 | US14c | Owatona | 7 | 40 | yes | crosses I-35 |
| US | 14.4 | US 14 | US14d | Janesville | 2 | 5 | no | |
| US | 14.5 | US 14 | US14e | Mankato | 9 | 15 | no | |
| US | 52.1 | US 52 | US52a | Zumbrota | 3 | 5 | no | |
| US | 52.2 | US 52 | US52b | Cannon Falls | 2 | 4 | no | |
| US | 52.3 | US 52 | US52c | Cannon Falls | 1 | 2 | no | |
| US | 52.4 | US 52 | US52d | Hampton | 4 | 2 | no | |
| US | 53 | US 53 | US53a | Eveleth | 1 | 1 | no | |
| US | 169.1 | US 169 | US169a | Mankato | 4 | 3 | no | |
| US | 169.2 | US 169 | US169b | Le Sueur | 1 | 1 | no | |
| US | 169.3 | US 169 | US169c | Le Sueur | 1 | 1 | no | |
| US | 169.4 | US 169 | US169d | Belle Plaine | 1 | 3 | no | |
| US | 169.6 | US 169 | US169g | Elk River | 1 | 3 | no | |
| US | 169.8 | US 169 | US169h | Princeton | 4 | 15 | no | |
| US | 169.9 | US 169 | US169i | Milaca | 1 | 4 | no | |
| MN | 1007.1 | MN 7 | MN7a | St Louis Park | 2 | 2 | yes | spur to MN100 |
| MN | 1007.2 | MN 7 | 7b | Minnetonka | 2 | 2 | yes | crosses I-494 |
| MN | 1013 | MN 13 | MN13a | Burnsville | 2 | 3 | yes | crosses I-35W |
| MN | 1015.1 | MN 15 | MN153060 | Tenmile Corner | 1 | 2 | no | |
| MN | 1015.2 | MN 15 | MN1560 | Madelia | 3 | 4 | no | |
| MN | 1015.25 | MN 15 | MN15b | St Cloud | 2 | 7 | yes | crosses I-94 |
| MN | 1015.3 | MN 15 | MN15c | Sauk Rapids | 1 | 1 | no | with US10b a tri-spur island |
| MN | 1023.1 | MN 23 | MN23a | Wilmar | 4 | 8 | no | |
| MN | 1023.2 | MN 23 | MN23b | Paynesville | 2 | 5 | no | |
| MN | 1030.1 | MN 30 | MN3060 | Saint James | 3 | 6 | no | |
| MN | 1036.1 | MN 36 | MN36a | Stillwater | 1 | 2 | yes | extends WI motorway |
| MN | 1036.2 | MN 36 | MN36b | Stillwater | 2 | 3 | no | |
| MN | 1036.3 | MN 36 | MN36c | Oakdale | 3 | 2 | yes | crosses I-694 |
| MN | 1051 | MN 51 | MN51a | Roseville | 2 | 1 | yes | crosses MN36 |
| MN | 1055 | MN 55 | MN55a | near MSP | 2 | 4 | yes | extends MN 62, but is 62 Eway? |
| MN | 1065.1 | MN 65 | MN65a | Blaine | 1 | 2 | no | |
| MN | 1065.2 | MN 65 | MN65b | Cambridge | 1 | 6 | no | |
| MN | 1101 | MN 101 | MN101a | Rogers-Elk River | 5 | 10 | partial | N bound has link from I-94 (North Bypass) |
| MN | 1371.1 | MN 371 | 371a | Little Falls | 2 | 8 | no | with US10c a tri-spur island |
| MN | 1371.2 | MN 371 | 371b | S of Baxter | 1 | 4 | no | |
| MN | 1371.3 | MN 371 | MN371c | Pequot Lakes | 1 | 4 | no |
Useful query
The overpass turbo Wizard query MN_Mway_island=* in Minnesota will locate all segments that have been tagged as describe above.
The query output can be enhanced with formatting. Add this line out of the generated "out body;"
{{style: way {text: eval("tag('MN_Mway_island')") } }}