Proposed features/Relation:tmc/TMC Points

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TMC Points
Status: Proposed (under way)
Proposed by: MHohmann
Tagging: type=tmc:point
Applies to: relation
Definition: TMC point locations
Rendered as: No particular rendering
Drafted on: 2014-01-18

This is the first stage of the TMC proposal. Goal of the overall proposal is to find a simple, useful, understandable and easily maintainable mapping scheme for TMC location codes. These codes allow a connection between TMC traffic guidance messages and OSM objects, so that OSM based navigation systems can calculate their routes under consideration of traffic messages. Goal of this first stage is to find a mapping scheme for the most simple TMC locations, which are points such as junctions or POIs.

Description

In the first stage of the TMC proposal only TMC point locations are to be mapped. These can be either isolated points, which are not connected to the road network, intermediate points along a single road such as bridges or tunnels, or junctions between several roads. Each TMC point location, which is uniquely identified by a country ID, table code and location code, should correspond to exactly one TMC relation in OSM. Some places, such as motorway intersections, have more than one location code - one for each motorway. These should be mapped using more than one TMC relation, one for each location code.

There can be two types of members in a TMC point relation:

  • Nodes on a road - For TMC points which are part of the road network these nodes mark where this point is located along the road. For larger structures, such as motorway intersections, they mark beginning and end of these structures as seen by a driver on that road. Up to four nodes should be mapped - beginning and end of the structure for each driving direction.
  • Infrastructure - Some TMC points, in particular isolated locations which are not part of the road network, correspond to infrastructure such as fairgrounds, stadiums, or roadside infrastructure such as rest or service areas. These elements of infrastructure should also be included as members of a TMC point relation.

Motivation

The tagging scheme for TMC point locations as proposed here is designed to be as simple as possible, so that the effort required to map TMC points is low. Every TMC point can easily be found using the coordinates, name and description provided in the TMC location code list.

Already this simple tagging can be used for routing / route planning with TMC messages. With TMC points connected to OSM nodes on the corresponding roads a router can easily find all TMC points which are passed on the calculated route, and filter TMC messages accordingly before providing them to the driver. Certain messages such as road closures or blockages may also cause the router to avoid the corresponding points and trigger a new route calculation based on this information. Similarly, also messages which concern closed / blocked rest or service areas or other types of infrastructure can be used to guide the user to a different location, if necessary.

Tagging

Every TMC point, which is uniquely identified by a country ID, table code and location code, should be mapped using one relation tagged as type=tmc:point. The members and tags of this relation should be as follows.

Relation members

A TMC point location may contain two different types of members: nodes on the road which are used for navigation, and elements of infrastructure, which may be affected by TMC messages.

Nodes on the road

Schematic of a motorway intersection

Every TMC point location which is part of the road network has exactly one associated road. The corresponding TMC point relation in OSM should contain up to four nodes on this road. These nodes mark the beginning and end of the structure described by the TMC point location. For example, if the TMC point is a bridge on a segregated highway, the four nodes should be the end nodes of the bridge in OSM. For a bridge on a non-segregated highway there are only two nodes at its ends. For a crossing of two non-segregated highways there is only one node.

For a motorway intersection, this situation is shown in the schematic. Each motorway is represented in TMC by a linked list of TMC point locations which mark junctions, intersections, service areas and similar points along the motorway. Each TMC point can belong to only one such list, and thus to only one motorway. At an intersection two motorways meet, therefore it has two TMC location codes, one belonging to each motorway. Consequently it should be mapped using two TMC relations, one for each TMC location code. Each relation should contain four nodes as members, which mark the first possibility to leave the motorway, and the last possibility to join the motorway. These nodes should be part of the same motorway as the TMC point location. In this case the blue motorway contains a TMC point location whose relation should contain the nodes A-D as members, where the motorway links meet the main carriageway. Similarly, the red motorway contains a TMC point location which should be mapped with a relation containing the nodes E-H.

In some situations there may be fewer nodes:

  • On a segregated highway / dual carriageway / motorway, there are two lanes / OSM ways. On each of these lanes two nodes should be members of the TMC point location. They are located where the first and last link way meet the lanes, or at the first and node of the structure (bridge, tunnel).
  • On a non-segregated highway there are no separate lanes / OSM ways. Therefore only two nodes mark the begin and end of the structure described by the TMC point location.
  • If the driver passes by only one node (for example, because he crosses a non-segregated highway), it is both the first and last node of the structure. On a segregated highway there are thus only two nodes.
  • Finally, on a non-segregated highway, which is crossed by another non-segregated highway, there is only one node (unless there are separated turn lanes).

The role of these relation members should always be empty.

Infrastructure

Elements of infrastructure which belong to TMC points may be service or rest areas (including parking spaces, restaurants, gas stations, motels) or tourist attractions, see TMC/Location Code List/Location Types#Point location types for an overview of possible point location types. OSM elements which may be affected by TMC messages should be included in the corresponding TMC point relation. These include in particular:

Relation members should have the following roles:

  • positive if the feature is available only to drivers on the positive side of the road (driving towards the positive offset).
  • negative if the feature is available only to drivers on the negative side of the road (driving towards the negative offset).
  • both if the feature is available independent of the driving direction.

Required tags

The following tags should be present in any TMC point relation:

  • type=tmc:point - Marks this relation as a TMC point.
  • table=* - Country ID (cid) and table code (tabcd) of the TMC location code table in the form {cid}:{tabcd} (e.g., 58:1 for Germany).
  • version=* - Version of the TMC location code table according to which this point is mapped (e.g., 13.0 for the table issued in Germany 2014).
  • lcd=* - Location code of this TMC point.
  • class=* - Class, type and subtype of this TMC point in the form {class}{type}.{subtype} (see TMC/Location Code List/Location Types#Point location types for a list of possible values).

Optional combinations

The following tags do not apply to all TMC points and should be used only when appropriate.

Names and references

Some TMC points have names listed in the location code tables. These can be tagged as follows:

  • name=* - Name of this TMC point.

Some TMC points contain the name or reference of a second road which intersects their containing road, such as the intersecting road at a motorway junction. This can be tagged as follows:

  • intersects=* - Name of the road intersecting at this TMC point.

If the TMC point is part of the road network, it may have an associated road name:

  • road_name=* - Name of the road containing this point.

Similarly, it may also have an associated road number:

  • road_ref=* - Reference number of the road containing this point.

TMC points such as motorway junctions or intersections may also include a junction reference number, which can be tagged as follows:

All tags containing names and references can be used to display additional information to the end user.

Presence depending on direction

Some TMC points are present / available only for drivers who are passing them by when they drive in one direction, but not in the other. Examples are service areas or rest areas along motorways, which are present only on one side of the road. This can be indicated as follows:

  • present=* - Specifies on which side of the road a TMC point is present.
    • present=positive - This point is present in the positive direction (for drivers driving towards the positive offset).
    • present=negative - This point is present in the negative direction (for drivers driving towards the negative offset).
    • present=both (default) - This point is present in both directions. This value need not be tagged.

Offsets

If the TMC point is part of the road network, the location code table contains its neighbouring points along the road it belongs to, called the positive and negative offsets. If they are present, they should be tagged as follows:

Positive and negative offset are always contained in the same table. It thus suffices to tag table=* only once to the whole relation.

Links to other TMC locations

TMC points may be linked to / part of other TMC locations in the same location code table. The location codes of these locations can be tagged as follows:

Examples

The following examples show some typical applications of the proposed TMC tagging scheme.

Motorway intersection - Hannover-Ost

This motorway intersection has two location codes in the location code list with cid=58 (Germany) and tabcd=1 (first table) - 10509 as a member of motorway A 2 and 12342 as member of motorway A 7. They should be mapped as follows:

10509 12342
Show TMC data Show TMC data
Relation 3497051 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx) Relation 3497050 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx)

Motorway junction - Bispingen

This motorway junction has two location codes in the location code list with cid=58 (Germany) and tabcd=1 (first table) - 12358 as a member of motorway A 7 and 28381 as member of L 211. They should be mapped as follows:

12358 28381
Show TMC data Show TMC data
Relation 3497049 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx) Relation 3497048 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx)

Roundabout - Heber

This roundabout has two location codes in the location code list with cid=58 (Germany) and tabcd=1 (first table) - 22793 as a member of B 3 and 28350 as member of L 170. They should be mapped as follows:

22793 28350
Show TMC data Show TMC data
Relation 3507088 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx) Relation 3507087 (XML, Potlatch2, iD, JOSM, history, analyze, manage, gpx)

Affected tags

No other tags are affected by this proposal.

Semi-automated import and quality assurance

In order to simplify mapping TMC point locations as far as possible and to minimize the mapping effort, a semi-automated import is to be used. This means that a script will generate most of the OSM data automatically. Mappers only need to review this data, possibly correct errors, add missing features and upload the result to OSM. Mappers need not enter any tags, such as TMC location codes, or names, by hand. The following steps can be done fully automatically, using the remote control feature of JOSM or Merkaartor:

  • Load and zoom the edited area.
  • Create a relation for a TMC point.
  • Enter all necessary tags.
  • Find candidates for the relation members.

This leaves only the following steps for the mapper:

  • Choose which nodes should be added to the relation.
  • Review the created name tags.
  • Upload the data to OSM.

The user need not check the location code numbers or other numerical data. A quality insurance check can perform the following tasks:

  • Check for completeness of the imported data and report missing relations.
  • Check for consistency of referenced location codes (order of offsets, segments, roads).
  • Check tagging against location code tables.
  • Check whether member nodes are on the correct road.

Comments

Please use the discussion page for comments on this stage of the proposal and the discussion page of the complete TMC proposal for comments on the overall TMC tagging concept.