> For the complete documentation index, see [llms.txt](https://docs.os.uk/os-downloads/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.os.uk/os-downloads/products/transport-network-portfolio/os-mastermap-highways-network-roads/os-mastermap-highways-network-roads-technical-specification/structure.md).

# Structure

The Road Network is a topologically structured link and node network made up of the following feature types:

#### Roads feature types

| Feature type  | Description                                                                                                                                                                                                    |
| ------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| RoadLink      | A line segment representing the general alignment of the carriageway of the road.                                                                                                                              |
| RoadNode      | A point connecting to at least one RoadLink, providing network connectivity.                                                                                                                                   |
| Road          | A Road defines the complete collection of references to RoadLink features defining the network topology which share the same road name and/or road classification number. For example, the A38 or Romsey Road. |
| Street        | A Street feature is the definition of the street as defined in the National or Scottish Street Gazetteer, made up of aggregated geometry with a unique identifier (USRN).                                      |
| RoadJunction  | A collection of RoadNodes that make up a named or numbered road junction.                                                                                                                                      |
| FerryLink     | A feature which represents a ferry route between two FerryNodes.                                                                                                                                               |
| FerryNode     | A feature representing the point at which a vehicle ferry route or section of ferry route starts or ends.                                                                                                      |
| FerryTerminal | A feature representing the point at which vehicle transfers from the ferry network to the road network or vice versa.                                                                                          |

<figure><img src="https://1897589978-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FcNpJpLP8RROUaWVQo5ea%2Fuploads%2FBOuxSdHesAdWCY37xSMt%2F5.png?alt=media" alt="Diagram showing relationships between Road Network feature types."><figcaption><p>Relationships between Road Network feature types</p></figcaption></figure>

OS MasterMap Highways Network has been built with the INSPIRE Transport Networks Data Specification as a basis. This has been extended to include the additional properties required by BS 7666-1:2006, defined within the NSG to ensure that conformance to both INSPIRE and BS7666-1:2006 can be achieved.

## Common attribution <a href="#bookmark23" id="bookmark23"></a>

Each feature within the OS MasterMap Highways Network will have the following common attribution:

* gml:id, gml:identifier and inspireId
* beginLifespanVersion
* inNetwork – this shall always be set to “OSHighwayNetwork”
* reasonForChange
* validFrom

{% hint style="info" %}
This is assigned a nilReason value “unknown” for most features.
{% endhint %}

In addition, many of the attributes which have been inherited from the INSPIRE Transport Network model have a stereotype of ‘voidable’, for example “beginLifespanVersion”. Where these attributes have not been populated there is a requirement to give a reason for this. This will be specified in the GML through an attribute called “nilReason”.


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