> 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/~/changes/AJZwzCsyrD9hiTbOxIbO/identifiers/os-open-linked-identifiers/os-open-linked-identifiers-technical-specification/roadlink_toid_street_usrn_8.md).
# RoadLink\_TOID\_Street\_USRN\_8
This document aims to provide all the information to evaluate if the method of associating the respective identifiers is suitable for your needs. These identifier relationships have been extracted from existing premium products and are presented in a standalone table for easy and open access to the information. It describes which product the information was extracted from, what information was extracted and how the source product derived the original association between the identifiers.
Identifiers displayed on OS Map data showing RoadLink and Topographic area feature types
## Relationship Extraction
This relationship is between the Topographic Identifier (TOID) of the RoadLink features and the Unique Street Reference Number (USRN) of Street features in *OS MasterMap Highways Network*.
A USRN is an 8-digit unique and persistent identifier for a street assigned by a Roads Authority or Highway Authority. Where possible, the geometry of Streets provided by the Roads or Highway Authorities is spatially matched to the geometry of OS RoadLink(s) and an aggregated geometry of the RoadLink(s) will be provided in the *OS MasterMap Highways Network*.
This relationship is extracted using the reference to the RoadLink(s) which have been matched to the Street
feature in the ‘link’ attribute within the *OS MasterMap Highways Network – Roads* product following its
release. This means that this relationship will not include all USRNs in *OS MasterMap Highways*, as Street features that have not been matched to an OS RoadLink will be omitted.
## Correlation Method
The relationship is determined by the link reference within *OS MasterMap Highways Network*, demonstrating the RoadLink feature(s) of which the matched Street features are composed. Where possible, the geometry of Streets provided by the Roads or Highway Authorities is spatially matched to the geometry of OS RoadLink(s) and an aggregated geometry of the RoadLink(s) will be provided in the *OS MasterMap Highways Network*.
As this relationship is determined using a single source product, the version information provided will always be the same as the version of the feature used to create the correlation.
A Confidence Value is assigned to indicate the reliability of the version information provided in this product in relation to the version of the features used to form the correlation in the original product. The Confidence Value is given for each relationship, which will always be defined in this relationship as:
| Confidence Value | Definition |
| ------------------------------ | ---------------------------------------------------------------------------------------------------------- |
| Version information is correct | The version information provided is the same as the version of the feature used to create the correlation. |
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