Part 2: Routing software and data options
Software Options
To generate any routing analysis specialist software is required. There are various solutions available and those described are considered to be the most popular across the public sector. Consideration has also been given to open source software although the options are limited and are considered more complex to implement. The traditional solutions for routing analysis have been using desktop GIS software. However, these are reliant on having appropriate hardware available. As an alternative several web-based services are also available.
CadCorp – CadCorp SIS Desktop incorporates a routing engine which supports both OS MasterMap Highways and the NGD Transport Theme data and includes tools for loading and building a network dataset from GML or GeoPackage. - https://www.cadcorp.com/.
Manifold – Although Manifold has a routing extension its support for GML is poor although it does read MapInfo TAB files. However, the software does not utilise turn restrictions, and other routing information - http://www.manifold.net/.
Network Analyst – Is an extension to ESRI’s ArcGIS Pro desktop software and can be used to solve complex routing problems. However, data models used to define network data are often complex; to help users overcome this ESRI have developed additional tools to assist users in creating and building networks. http://www.esri.com/software/arcgis/extensions/networkanalyst/. Tools are available to create networks from both OS MasterMap Highways and NGD Transport Theme data.
RouteFinder for MapInfo – Produced by Routeware (http://www.routeware.dk/index.php) and distributed in the UK by Higher Mapping Solutions and CDR Group. A tool is available to convert Highways GML into a TAB file suitable for routing. Widely used across the Local Government Community and is incorporated into Capita’s One system for school transport planning.
StatMap – eVO Routing Services includes support for OS MasterMap Highways including tools to load and maintain a routing network. - https://www.evo.statmap.co.uk/routing
TRACC - Produced by Basemap and widely used across the Public Sector to look at public transport impacts on service location - http://www.basemap.co.uk.
Data Options
To create a routable network a variety of data types are required:
Geometric network – most commonly this would be topologically structured road centrelines. However, foot paths, waterways or cycle paths may also be incorporated.
Restrictions – to create a full network, routing restrictions such as no-turns and one-ways are required.
Speed limits – differing speeds will need to be applied to network links depending on several factors such as road classification and whether it’s an urban or rural environment. These are important for developing time-based applications.
Network Data
The OS MasterMap Highways Network is Ordnance Survey’s premium large scale roads dataset and contains a topologically structured network line representing the centreline of carriageways for all major and minor roads in Great Britain, along with road names and numbers. In addition, the data contains information on routing restrictions such as one way streets and banned turns which makes it an ideal choice in routing applications. Currently this is the preferred option for detailed analysis and further details about the data can be found at - https://www.ordnancesurvey.co.uk/business-and-government/products/os-mastermap-highways-network-products.html.
In addition to the road features, the paths data provides a detailed path and alleyway network that can be linked to the road network lines from Highways to create a walking or cycling network.
Restrictions
Both the OS MasterMap Highways Network and OS NGD Transport data include routing and asset management information (RAMI) describing restrictions, permissions and other information relevant to the network. The information is provided in the form of rights and restrictions:
Access Restrictions
Turn Restrictions
Restrictions for vehicles, including height, weight, width and length restrictions
Highways dedications, providing information on the type of users who have access to a particular network section, including byways, cycle tracks and bridleways
Additional information is also part of the Path Network and is structured in a similar way, including details of steps and ramps.
Other data that would be useful in creating a network include:
Cycle crossings
Pedestrian Crossings
Traffic Lights
Although some local authorities do make data available for these on their websites, no national data sets are currently available.
Speed Data
Speed data is an important part of generating a network for detailed analysis as it provides the content for journey time analysis as the speed one can travel along a link will determine how far can be traveled in a given time. There are three types of speed data:
Legal speed limit – as defined by road signage maintained by the local authority. However restrictions within these limits apply to different vehicle types, as detailed on the DfT website - https://www.gov.uk/speed-limits.
Derived or average road speeds – these are harder to define and vary depending on time of day. There are several sources of these, however many are only commercially available as seen as a valuable part of a network data set.
Estimated road speeds – based on speed limits, road classification and personal interpretation.
The RAMI collection in OS NGD Transport contains Average and Indicative speed information for all roads in Great Britain. These are:
A historic average speed in kilometres per hours (kph). In this context, 'historic' means that the average speed data was collected over a six-month period for the selected road link. Average speeds are provided in different time periods for each road link. A single day (i.e. a 24-hour period) is split into 8 time periods Monday to Friday (MF) and 6 time periods Saturday to Sunday (SS), for example, Monday–Friday (MF) 07:00–09:00, Saturday–Sunday (SS) 14:00–19:00. There’s a separate attribute for each time period. For Road Links that can be traversed in both directions, ‘In Direction’ and ‘Against Direction’ attribute values are populated for average speed. For one-way Road Links, only one of these attributes will be populated, dependent on the directionality of digitising of the Road Link
An indicative speed limit. This is an indication of the maximum speed limit for vehicles. T A single indicative speed limit value (based on the value that applies to the majority of each Road Link section) is provided in both miles per hour (mph) and kilometres per hour (kph).
Local Knowledge
Another useful source of information is your own local knowledge. This may be knowledge of travel restrictions at certain times of day, e.g. some schools operate a voluntary one-way system to aid congestion at the start and end of the school day. This information can be stored in a table separate from your network. The Highways data contains a TOID as a consistent identifier and can be used to link between data sets.
Other Useful Information
OS MasterMap Sites Layer – This is part of the OS MasterMap Topography Layer and provides an outline of features including an educational establishment, medical facility and transport facility. The data includes the access points for the site with a link to OS MasterMap Highways. These can be used to further enhance your data in joining the network to addresses and other features across the landscape.
Urban / Rural areas –OS MasterMap Highways data does not include a definition of whether a link is within a rural or urban area. By using the urban extents from other Ordnance Survey products, such as OS Vector Map Local, it is possible to add this as an additional attribute. Although some software offers an option to add this as part of the creation and build of a network. The simplest way to do this is by performing a spatial intersection between the road link and urban extent data. The result can then be used to classify a link as either urban or rural and assign a default value accordingly. However, where a link falls within both classifications it can either be split into 2 parts or classified according to which area contains the longest part of the link.
Creating a network hierarchy can improve network efficiency by preventing routing software from using the full network when calculating routes. For instance, calculating a journey from London to Glasgow does not need to use all the minor roads along the route. Developing a hierarchy will allow the software to quickly find only the major network and use this to determine when the destination is found. Previously, DfT generated a major route network as part of the legacy Transport Direct web service. This is known as the Transport Direct Routing Network and can be downloaded from Github - https://github.com/Deptfortransport/TDRN. Although the original data is based on OS MasterMap Integrated Transport Network, as it comprises a list of unique identifiers or OS MasterMap TOIDs that can be used to add an additional attributes to a network.
Multi-modal Transport
When reviewing services such as the location of a GP Surgery or specialist health clinic, journeys by different transport modes, such as walking, public transport and cycling are required. It is possible to join the different elements of either OS MasterMap Highways or NGD Transport data to create different types of networks. In addition to this public transport may be added. Railway stations form part of several Ordnance Survey products and Sites layer contains both the outline of a station site and its access points.
However the OS Multi-modal Routing Network has been designed for use in this type of analysis. Public Transport information can be linked to the data from sources such as Traveline - http://www.traveline.info/. Although bus stations are included in OS data bus stops are not. These can be obtained in a geographic form from DfT’s NATPAN data - http://data.gov.uk/dataset/naptan, which also includes railway stations and airports.
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