Minnesota/Minnesota highway classification/Motorway island survey results

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This page gives the results of a survey done asking OSM mappers their opinions about how to classify some existing motorway-islands. This page provides recommendations only for the specific motorway islands studied and is not a general guideline for the future. General guidelines may be proposed, but not on this page. This page provides the results of the survey, identification of participants in the discussion, and a description of the methodology used along with the timeline.

An important thing to understand is that this island-by-island evaluation was done after there appeared to be no consensus on the general question about what distinguishes a motorway island from a trunk highway and/or expressway. This survey was done with the hopes of at least classifying the existing motorway islands so they could be classified in an agreeable way.

Survey results

Following is a simplified table including a summary of comments made by nine different mappers. The highest level view of this can be seen in these three columns:

  • Island ID: the identifier of the specific motorway island (see Methodology section for more information about Island IDs)
  • Reason: the specific reasoning the author bases the highway classification type proposal on (the reason codes are explained later)
  • Type: the proposed highway type for this motorway island.

Other columns in the table are described after the table.

In this table, the last column contains italicized & bolded entries. That style is used to indicate that the type indicated is a proposal. The rest of the table is either factual or a good faith attempt to summarize opinions of other people.

Results of focused discussion of specific motorway-islands. Specific comments and proposed type based on discussion.
Highway Island ID Int Km J McG * Ian * Bob * J R P * Jumb * Clay * Turn * D W * Map A * Reason Type
US 2 US2a 4 15 MW trunk 1e MW A Motorway
US 10 US10a 1 3 MW 6c trunk 1d trunk 2a trunk 1d trunk 1d trunk 1d trunk 1d B Trunk
US 10 US10b 3 6 MW trunk 1e MW 6c A Motorway
US 10 US10c 5 8 MW trunk 1e MW A Motorway
US 10 US10d 3 5 MW trunk 1e MW A Motorway
US 14 US14a 1 3 trunk trunk 1e trunk D Trunk
US 14 US14a2 1 5 trunk 3a trunk 1d trunk 2b trunk 1d trunk 1d trunk 1d D Trunk
US 14 US14b 4 30 MW 6a trunk 1e MW 6b A Motorway
US 14 US14c 7 40 MW 6a trunk 1e MW 6b A Motorway
US 14 US14d 2 5 MW trunk 1e MW 6b A Motorway
US 14 US14e 9 15 MW trunk 1e MW A Motorway
US 52 US52a 3 5 MW trunk 1e MW 6b MW A Motorway
US 52 US52b 2 4 MW 6c trunk 1e MW 6b MW MW 5f MW A Motorway
US 52 US52c 1 2 trunk 2c trunk 1d exp 4a trunk 1d MW 5f trunk 1d Eway 4a, H H Trunk
US 52 US52d 4 2 MW trunk 1e MW 6b MW A Motorway
US 53 US53a 1 1 trunk 1a trunk 1d trunk 1b trunk 1d trunk 1d trunk 1d D Trunk
US 169 US169a 4 3 MW trunk 1e MW MW 7a A Motorway
US 169 US169b 1 1 trunk 3b trunk 1d trunk trunk 1d trunk 1d trunk 1d D Trunk
US 169 US169c 1 1 trunk 3b trunk 1d trunk trunk 1d trunk 1d trunk 1d D Trunk
US 169 US169d 1 3 MW 5a trunk 1d trunk trunk 1d trunk 1d trunk 1d trunk 1d C Trunk
US 169 US169g 1 3 MW 5c trunk 1d trunk trunk 1d trunk 1d trunk 1d trunk 1d B Trunk
US 169 US169h 4 15 MW 5a trunk 1e MW A Motorway
US 169 US169i 1 4 MW trunk 1d exp 4a trunk 1d trunk 1d trunk 1d trunk 1d MW G Motorway
MN 7 MN7a 2 2 MW 5a trunk 1e exp 4a C Trunk
MN 7 7b 2 2 MW 7d trunk 1e exp 4a I Motorway
MN 13 MN13a 2 3 MW 6c trunk 1e B Trunk
MN 15 MN153060 1 2 trunk 3c trunk 1c trunk 1c trunk 1d trunk 1d trunk 1d D Trunk
MN 15 MN1560 3 4 MW trunk 1e MW A Motorway
MN 15 MN15b 2 7 MW 7a trunk 1e MW A Motorway
MN 15 MN15c 1 1 MW E trunk 1d MW 7b MW E trunk 1d trunk 1d MW E E Motorway
MN 23 MN23a 4 8 MW 5d trunk 1e MW A Motorway
MN 23 MN23b 2 5 MW trunk 1e A Motorway
MN 30 MN3060 3 6 MW trunk 1e MW A Motorway
MN 36 MN36a 1 2 MW F trunk 1d MW MW F trunk 1d trunk 1d MW F F Motorway
MN 36 MN36b 2 3 MW 5c trunk 1e B Trunk
MN 36 MN36c 3 2 MW 5c trunk 1e MW A Motorway
MN 51 MN51a 2 1 MW 5a trunk 1e exp 4a trunk 1a trunk 1f MW C Trunk
MN 55 MN55a 2 4 MW 7c trunk 1e A Motorway
MN 65 MN65a 1 2 MW 7a trunk 1d exp 4a trunk 1d trunk 1d trunk 1d trunk 1d MW G Motorway
MN 65 MN65b 1 6 MW 7a trunk 1d exp 4a trunk 1d trunk 1d trunk 1d trunk 1d MW G Motorway
MN 101 MN101a 5 10 MW trunk 1e MW A Motorway
MN 371 371a 2 8 MW trunk 1e MW A Motorway
MN 371 371b 1 4 MW 5a trunk 1d trunk 1b trunk 1d trunk 1d trunk 1d trunk 1d C Trunk
MN 371 MN371c 1 4 MW 5a trunk 1d trunk 1b trunk 1d trunk 1d trunk 1d trunk 1d C Trunk

Further notes about this chart.

  1. The first four columns are information about the island: The specific highway; the specific island ID (see below for more information), the number of grade-separated interchanges this island has; the approximate length of the island in kilometers.
  2. Nine pairs of columns for the nine individuals that provided island- or set-specific comments after the focused discussion began. The nine participants are listed in the Participation section below. The first column of each pair is the specific recommendation made by the individual for the specific island (MW=motorway, exp=expressway, trunk=trunk). The second column in the pair is a summary of the reasons given by the individual for their recommendation. These reason codes are provided in a table below.
  3. The next to last column (Reason) provides the reason the author used to make the proposal in the last column. The reason codes are also summarized in the table below.
  4. One additional note: the last column does not call out expressways in particular. Presumably all islands with a Trunk proposal will be keyed as expressways.

The following chart lists the various reason codes. The chart includes a paraphrasing of the reasons given by the individuals choosing motorway, expressway, or trunk. Notes explaining the table are below the table.

Reason codes used in the table above
Group Code Explanation
Trunk ! 1a Too short
1b Isolated and short
1c Just an intersection
1d Has only one interchange
1e Less than a couple dozen miles (24mi~40km)
1f Has RIRO prior to first "median crossover"
Trunk 2a Very degraded from motorway definition
2b Likely to confuse people if coded motorway
2c Trunk now but should be monitored for planned upgrades over time
Trunk ? 3a Upgrade to motorway would lead to a mistake elsewhere
3b Borderline too short
3c Would accept upgrade to motorway
Expressway 4a This should be trunk with expressway=yes
Motorway ? 5a Long enough but ok but would accept trunk
5b Should possibly be motorway link
5c Will be upgraded to non island soon
5d This may have been expanded recently
5e At grade railroad crossing degrades this possibly to trunk
5f Together these two could be combined into larger island
Motorway 6a These two islands have been combined into larger island
6b Part of a larger system being built out
6c Expansion to longer island seems likely
Motorway ! 7a Long enough and has multiple grade separations
7b Spur to motorway system, not an island
7c Part of a longer motorway
7d Connected to a motorway network
Motorway A Local knowledge trumps 1e
Trunk B All but one for trunk trumps future (5c,6c)
Trunk C One Prefers motorway but trunk is acceptable (5a)
Trunk D All believe trunk is right
Motorway E After focused Slack discussion, consensus is motorway or motorway_link
Motorway F After focused Slack discussion agreed part of a larger motorway island in WI
Motorway G After focused Slack discussion, no disagreement with 7a assertion
Trunk H RxR between this segment and US52a argues for this to NOT be Mway
Motorway I No focused discussion but similar to US169i, MN65a, MN65b

Notes about the table above

  1. The top part of the table (1a-7d) provides paraphrases of the reasons given for the highway type classification.
  2. Groups with "!" seem to be strongly held opinions.
  3. Groups with "?" seem to be weakly held opinions in that there was either some hesitancy or the individual was willing to accept a different classification
  4. The bottom part of the chart contains reasons the author decided on the classification given. These reasons represent an attempt to balance the various individual's reasons.
  5. Of course, all paraphrases above can be improved. They are just a shorthand way of summarizing well articulated reasoning. Consult the discussion threads for details.

A special note about the the entire spectrum of opinions. There were two views that represented the "extreme" views.

  • As originally proposed, ALL motorway islands would be kept classified as motorways. There was no minimum length and no grade-separated intersection requirement.
  • The other view that surfaced in the focused discussion was that there are NO motorway islands in Minnesota that meet the minimum criteria articulated. See 1e where a minimum length to qualify as a valid motorway is a "couple dozen miles". The longest currently-mapped motorway island in Minnesota is approximately 40 kilometers, just over two dozen miles.

Reason A takes the view that there is sufficient local knowledge about the existing motorway islands that does not agree with the reason 1e. Needless to say, if reason 1e was more commonly held and applied here the proposed results would be far different.

Participation

The participants in the focused discussion are listed below.

Focused discussion participants (alpha sort by Slack ID)
Abbreviation Slack ID
Bob Bob G
Clay clay_c
D W David Wisbey
Ian ian
J McG Jackson McGough
J R P Joseph R P
Jumb jumbanho
Map A MapAdderz
Turn TurntSnacko

Additionally it should be noted that the total number of members of the #local-minnesota slack channel at this time (2/20/2022) is 34. Several of the channel members may have commented before the focused island discussion thread. Any additional input concerning the recommendations would be welcomed of course.

An outreach was done to mappers not using Slack to visit the wiki and/or participate in the Slack discussion. Direct OSM messages were sent and in some cases comments were made on changesets for some of the islands where it was possible to identify a mapper who made a classification change. The specific mappers who were contacted are: Aleg_Surta_Mapbox, bkreegs, Botogav, Brian Tang, ChrisBessert, Fluffy89502, GJF85, IBTTA_1, J L, Molandfreak, Mrninja2001, Mulad, NorthwestPAmapper, ntisdell, ridethehighway65, RocketTuna, Scottahemi, Spencer_MHD, swbr0502, The Don MN, Tornado9989, Yocomik. It is possible that some of the mappers did participate but were not recognized due to the difference in their OSM ID and Slack ID. One invitation is not mentioned above because that mapper did join the Slack conversation and the specific opinions are captured in the table above. For others in the list, no reply was made to either the direct message or any changeset comments. (Note that only a few change set comments were made, but all mappers above did receive direct OSM messages.)

Survey methodology

For the individual island survey the following method was used to identify islands:

An overpass turbo query was run to find every highway classified as Motorway in Minnesota. Anything that looked like an island was considered to BE an island. This resulted in some false positives such as spurs appearing to be islands and gaps caused by incomplete tagging. No attempt was made to prune these possibly false positive from the list.

For each suspected island a special key was added to OSM so the specific island could be more easily visualized. The key MN_Mway_island=* was applied to one side of the dual carriageway only, for the extent of the mapped motorway. The key was applied to every segment of that carriageway from the beginning the island to the end of the island. Searching on that key value pair makes it easy to see the extent of the island (at least on that side). The values for that key are the Island IDs in the table above. A specific overpass turbo query will show all of the highway segments with this key.

A discussion was started in Slack pointing to the islands and inviting individual opinions about each island.

Towards the end of the discussion a number of specific islands that seemed to be borderline cases were specifically identified and opinions were solicited. In general reasons A-D were figured before the very focused discussion took place. Reasons E and following were based on the more island specific discussions.

Timeline

The original proposal (call it version 1) was agreed and published on the Minnesota/Minnesota highway classification page on January 26, 2022.

Subsequently talk-us and Slack discussions took place, mainly discussing motorway islands.

The focused motorway-island discussion began was started in Slack on February 1, 2022. That discussion pointed to a wiki page cataloging and identifying the motorway-islands in Minnesota.

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