Tram definition: A rail track dedicated to the movement of passenger tram rolling stock within big towns and cities.
Understanding where tram tracks are present on the road network can provide useful information for maintaining both road and tram assets, understanding risk for road users sharing the same space as trams, and supporting transport network management.
Within the OS NGD there are several feature types which will allow you to view and analyse tram track information, each with their own design and intended use cases.
These are all found within the OS NGD Transport Theme and are listed below:
Tram presence attribution provided on the Road Link feature type.
A dedicated Tram On Road feature type to help you understand the extent of tram track presence on the road network.
A Network representation in the Railway Link feature type.
The following sub-pages give more detailed information about the above three representations and how they can be used, to allow you to decide which best suits your use case.
Within the OS NGD Transport Theme, in the OS NGD Transport Network Collection, the Railway Link Feature Type represents geometry of Great Britain’s Rail Network.
This feature type provides a routable network when used in conjunction with the Railway Node Feature Type. The Rail network includes tram tracks as well as train tracks. Trams can be identified by the description attribute, which describes the nature of the railway the feature is representing (for example, description = Tram).
The Railway Link feature type provides a generalised geometry for the rail network of Great Britain. The generalisation of the rail network ensures full connectivity between relevant rail nodes. Rail track generalisation can be typically 3 or 4 sets of rail tracks represented as one link, for example multiple siding tracks. However, this may not always be the case, for example tracks that pass either side of a station platform are normally included to ensure connectivity at a station.
Routing along the rail network, including trams
Visualising track centreline geometry. Railways Links provide the generalised geometry of rail and tram tracks
Identifying which road links have tram track on them
The Tram On Road Feature Type can be found in the OS NGD Transport Network Collection of the OS NGD Transport Theme. This feature type provides a stand-alone geometry to depict where tram tracks are on the road network. This geometry is derived from the Road Link Feature Type and as a result will be coincident with the Road Link features.
A Tram On Road feature is provided where a tram track is present on the road network. The feature represents the section of the Road Link where there is a tram track closely associated with it. When comparing this geometry to the Road Link feature type you would expect to find ‘gaps’ in Trams on Road features where tram tracks do not coincide with the entire Road Link.
All Tram On Road features have a linked identifier (Road Link ID attribute) to the Road Link feature they are associated with.
The Tram On Road Feature Type aims to give a granular depiction of the where tram tracks exist on a road link.
To create the Tram On Road Feature Type we have used an algorithm which assesses Railway Links, road surface polygons (part of the OS NGD Transport Features Collection: Road, Track, and Path topographic data) and Road Links.
The algorithm takes Railway Links with 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. A Tram on Road feature is created to indicate exactly where the tram interacts closely with the Road Link, with its geometry derived from the Road Link.
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.
Understanding where (the extents of) tram tracks are on the road network
Visualisation of the physical extents of where tram tracks are on roads
Routing along the tram network. Tram on Road consists of a discontinuous set of geometries, which is not a routable network. Instead, the Railway Link feature type will help with this use case.
A tram track centre line. Tram on Road uses Road Link geometry. The Railway Link feature type provides geometry for the generalised rail network, including tram tracks.
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
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.
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.
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.
