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OS MasterMap ITN Layer support

The ITN Layer is a dataset of Great Britain's road network from motorways to urban paths. It includes traffic restrictions such as one-way systems and low bridges.

What is the Integrated Transport Network Layer?

The OS MasterMap® Integrated Transport Network (ITN) Layer is the definitive national road network for Great Britain. It provides a flexible foundation for publishing, transport, telematic and asset-management solutions and can be fully integrated with all OS MasterMap layers; for example, within OS MasterMap Address Layer for to-the-door routing.

If a satellite navigation device is routing vechicles wrongly can I make changes to ITN to correct this?

We can check the road designation- A road, minor, private,- and if there are any physical or signed restrictions in place though the actual routing from one destination to another is determined by the software and data providers for SatNav devices.

Please see our satellite navigation page for more background and links to report errors to manufacturers.

What level of detail does the ITN Layer offer?

The OS MasterMap® Integrated Transport Network (ITN) Layer is the definitive national road network for Great Britain. It provides a flexible foundation for publishing, transport, telematic and asset-management solutions and can be fully integrated with all OS MasterMap layers; for example, within OS MasterMap Address Layer for to-the-door routing.

How is the road network described in the ITN Layer?

In OS MasterMap Integrated Transport Network (ITN) Layer individual sections of road are represented by RoadLink features, which show the general alignment of the carriageway. RoadLink features have attribution to describe the type and nature of the road.

Road type classifications include motorway, A road, B road, minor road, local street, private road – publicly accessible, private road – restricted access, alley and pedestrianised street. The nature of the road classifications includes single carriageway, dual carriageway, slip road, roundabout and traffic island.

The connectivity is described by relationships at the ends of the RoadLink features and a relative third dimension is included to allow for roads crossing at different levels.

Named and numbered roads are represented by compound features referencing the RoadLink features that represent the extent of the road.

How is information about routing represented in the ITN Layer?

In OS MasterMap Integrated Transport Network (ITN) Layer information that may affect a driver's choice of route is represented by additional features that reference the base network. This is known as Road Routing Information (RRI). These features describe physical restrictions, permissions and other signed information relevant to drivers.

The restriction information is not applied to the base network, but is referenced. This allows the range of information collected to be extended in the future and minimises the impact on customers not concerned with routing information.

The main categories of restriction information captured are as follows:

  • One way
  • No entry
  • Access prohibitions
  • Access limitations
  • Turn restrictions
  • Mandatory turns
  • To whom the restrictions apply and any time constraints are also captured
In the ITN Layer, why is the road name not attributed to links?

Because a named or numbered road is a definable entity, the OS MasterMap Integrated Transport Network (ITN) Layer considers it to be a discrete feature. The ITN Layer adopts a relational structure for the data; road link features describe each section in the road network and the road feature represents the named or numbered road. Every road feature will reference the TOID of one or more road link features that represent the alignment of the road.

How many times does a road name appear in the ITN Layer data?

In OS MasterMap Integrated Transport Network (ITN) Layer, a road feature will occur once for each named road within a specific area in the road feature and is linked to the road link features that make up that road by reference to the constituent road link TOIDs. Numbered roads are created as single features, no matter how fragmented they are; for example, there are 1 017 occurrences of Green Lanes but only one B3181.

What is the data format for OS MasterMap ITN Layer?

The data format for OS MasterMap Integrated Transport Network (ITN) Layer is GML v2.1.2.

Will there be links from the ITN Layer to the Local Street Gazetteer (LSG)?

The structure of OS MasterMap allows for data association; therefore, other datasets, such as LSG data, can be linked to the Integrated Transport Network (ITN) Layer TOID. Some highway authorities have used the ITN Layer to create a baseline LSG.

What network features and attribution are available with the ITN Layer and RRI?

The network features and attribution available with OS MasterMap Integrated Transport Network (ITN) Layer and Road Routing Information (RRI) are as follows:

  • Road link classifications - Motorway, A road, B road, minor road, local street, alley, pedestrianised street, private road – publicly accessible, private road – restricted access.
  • Road link types - Dual carriageway, single carriageway, slip road, roundabout, traffic island, traffic island at junction, enclosed traffic area.
  • Ferry network - Ferry terminals, ferry link and ferry node.
  • Routing information - No turn, mandatory turn, no entry, access prohibited to (specified vehicle types), access limited to (specified vehicle types), height restrictions, fords, mini roundabouts, traffic calming, gate, tolls, bridge over road, firing range, through route, severe turn.
What is the definition of public and private roads in the ITN Layer?

The attribution of public and private roads on Ordnance Survey products has traditionally been based upon an assessment of the accessibility and nature of the road by the data collector. Ordnance Survey attempts to record this information accurately, however Ordnance Survey does not decide, and ITN is not the definitive record of, either the responsibility for maintenance or the accessibility for roads. This information is within the remit of the Local Highway Authority.

Normally no formal enquiries surrounding ownership and/or responsibility for maintenance were made. In recent years Ordnance Survey has received feedback from local authorities, via the Department for Transport (DfT), indicating if any roads need to be reclassified from public to private or vice versa. Where these do not clash with Ordnance Survey specification such changes are incorporated into Ordnance Survey vector roads products, such as OS MasterMap Integrated Transport Network Layer (ITN).

What is the difference between "Private Road - Publicly Accessible" and "Private Road - Restricted Access"?

"Private Road - Publicly Accessible"

A privately-maintained road or a road within a property boundary where access by the public using a motor vehicle is considered usual for at least some part of the day. For example, a road within a hospital, sports centre or school. They may extend through a site if more than one entrance exists. If only one entrance exists they are normally created to extend to the principal building within a single site or the boundary of the last property served for features accessing more than one addressed or otherwise identifiable property.They may be captured outside this definition if required to provide connectivity to a track or path.

"Private Road - Restricted Access"

A privately maintained road or a road within a property boundary where access by the public using a motor vehicle is restricted by physical (for example a gate)administrative (for example a sign) means or is not considered usual where you could expect to be challenged as to your use of the road. For example, roads within a military base, an oil refinery, within a private residential garden or leading to two private properties. Such roads are captured only where they exceed 100 m in length or serve more than one addressed or otherwise identifiably separate property. Roads are normally created to extend to the principal building within a single site or the boundary of the last property served for roads serving multiple properties. Two exceptions to this exist:

  • where a track or path exists that the road is connected to, the road must be extended to that point; and
  • where roads within a private residential garden extend for more than 100 m from the property boundary.

Walkers, cyclists or horse riders may or may not be able to use a Private Road, ITN does not currently record this information.

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