Tram attribution on Road Link
Background
Within the OS NGD Transport Theme, in the Transport Network Collection, the Road Link feature type represents a line geometry for Great Britain’s road system.
This feature type provides a routable network, when used in conjunction with the Road Node feature type. Specific tram attribution is provided against a road link (schema version 3.0 onward) as described below.
Attribution indicating the presence of trams:
The extent of tram track present on the Road Link, either full or partial
The direction the tram track applies, in relation to the direction of digitisation of the Road Link
Technical detail
To determine tram presence information on roads, we have used an algorithm which assesses Railway Links, road surface polygons (part of OS NGD Transport Features Collection: Road, Track and Path topographic data) and Road Links.
The algorithm takes Railway Links with the description value ‘Tram’ and applies a buffer to identify which road polygons intersect and are therefore closely associated with these Tram links. All Road Links within the intersected polygons are then candidates for inclusion in the dataset. Further logic within the algorithm determines which Road Links are attributed with tram presence. The entire Road Link receives the attribution of ‘partial’ or ‘full’ presence.
Note that certain types of tram link are not considered by the algorithm, including "preserved", "static museum" and "funicular". These types of tram link are not required for transportation and navigation use cases, as they mainly serve a leisure purpose.
Examples of uses this data supports
Identify all road links that have a tram track on them.
Support asset management uses cases by identifying whether a Road Link has a tram track on it which will impact street works and reinstatement jobs.
Support transport network management by identifying which Road Links will be impacted during tram track maintenance or incidents on the tram network, and what this would mean for wider traffic flows, road closures and diversions.
Examples of uses this data doesn't support
Visualisation use cases to depict the exact extent of the tram tracks.
Routing along the tram network – the Railway Link feature type will help with this use case.
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