This tutorial shows how to perform a public transport network analysis using the TravelTime API. Here, we use the TravelTime add-in for ArcGIS Pro to do an urban network analysis. You are encouraged to download the add-in and use the API yourself, following the steps from this tutorial.
Introducing the TravelTime add-in for ArcGIS Pro
The TravelTime API functionality can be accessed within ArcGIS Pro using the TravelTime add-in. This means you can create isochrone maps and do routing inside ArcGIS Pro using the API’s capabilities.
An add-in is a customisation, such as a collection of tools on a toolbar, that plugs into an ArcGIS Desktop application to provide supplemental functionality for accomplishing custom tasks, in this case building time travel maps using isochrones, or filter by journey time and routing.
Downloading and installing the add-in
The add-in can be downloaded here. After signing up, a download of the add-in starts automatically. Opening the downloaded file will install the add-in. After opening ArcGIS Pro, head over to Settings on the bottom left of the screen and click Add-in Manager on the menu left.
If you’ve instead opened a new or existing Project file in ArcGIS Pro, click the “Project” dropdown menu in the upper left of the screen and then “Add-in Manager”. The TravelTime add-in should now be listed under My Add-ins.
In the Ribbon interface of the main application, a new menu is displayed, called TravelTime platform, that shows multiple menu items when clicked.
Clicking the second item from the left shows the TravelTime Toolbox in the Catalog window on the right, offering extended functionality that will be used in this tutorial:
We now have everything we need for our geospatial network analysis.
Mapping access to public transport using the TravelTime add-in for ArcGIS Pro
The TravelTime add-in can tell us more about the accessibility of a public transport network. For example, we can create isochrones for an entire public transport network, showing the size of a catchment area around a station (bus/underground/train).
To do this, we need point data of a public transport network of choice, in this case, the city of London. For the following analysis, a feature layer is used, showing underground, overground and national rail stations and lines in London.
The layer can be found by doing a content search in the Catalog pane in the Portal tab and choosing the ArcGIS Online cloud symbol. Feature layer data can be dragged and dropped in the map window where it is displayed instantly. Here is a description from ArcGIS Online of the dataset:
The London Transport feature layer contains points and polylines, but here we only need the points that display the different rail and underground stations that constitute our public transport network.
The TravelTime add-in can now be used with the feature layer to show different catchment areas. We can create isochrones around the different stations showing 10-minute walking catchment areas using the TravelTime toolbox and creating a Time Map (Simple):
The result is a map showing a union of all different catchment areas, which is a better visualisation than showing only the individual and overlapping areas using the “NORMAL” option under Result aggregation:
Repeating this process multiple times, we can create the 30-minute walking catchment areas in purple, with both 20- and 10-minute walking catchment areas on top:
Finally, for an even better understanding of the areas that fall outside of the 30-minute catchment areas, we can create an overlay of a map using the inner and outer boundaries of the different districts in London, using a feature layer from ArcGIS Online called “statistical gis boundaries”. This layer contains multiple polygon layers, but for now, we only use the London_Ward_CityMerged and overlay it with the 30-minute catchment areas:
Using the Erase geoprocessing tool, with the London boundary polygons as input and the 30-minute catchment areas as Erase Feature, we create a map that shows these areas even better:
Here is a close-up of the same map showing East London:
If we were interested in creating a list of the postal codes that are contained within these areas, we can add another feature layer from ArcGIS Online with all London postal code districts (“LFB Postcode Districts”), and run the Intersect tool as follows with the results created earlier:
Running the tool creates the following output with the rows of the newly created layer and attribute table showing the individual postal codes that belong to the multiple polygons inside of the different areas that are not within 30 minutes walking of our tube and train stations:
What the analysis shows
The urban network analysis of the different walking catchment areas around the different transport network stations shows different areas at the edges of London that cannot be reached within 30 minutes walking. These are the uncovered areas by the Time Map tool, such as the one indicated by the arrow on the 20-minute Time Map. More of such areas can be seen in West London, as well as one in East London (indicated above with red arrows).
Maps such as these can be used to improve public transport infrastructure and for deciding where future stations should be located. Additionally, using these maps overlaid with population makes it possible to find what percentage of the population is not within a 10/20/30 minute walk of an underground/metro station. With a new station opening in a new location, this percentage could fall, so that more people can reach a bus/train/metro station within 10/20/30 minutes.
Improving public transport infrastructure using geospatial network analysis
Using the TravelTime routing tool, we can analyse how people move through a specific transport network. Taking a sample of postcodes across London from highly residential areas, we can calculate the routes from these to key areas where lots of people work, such as City of London and Canary Wharf.
The data on this map can be used to manually create a set of points inside highly residential locations so they can be geocoded using the ArcGIS World Coding Service, after which we can calculate the routes to a work location.
First, we look for a feature layer with population density data, using the “London population density for different geographies” feature layer from ArcGIS Pro and adding symbology for the different areas, using the smallest geographical areas available (LSOAs). The areas marked in red have the highest population density:
Next, we create a new feature class through the Catalog pane in our geodatabase for five to-be-created points and add this to our map. Next, we configure a template for our points, using blue thick pins and add five points in highly residential areas:
Using the Reverse Geocoding tool, we can add addresses to the five newly created points. This info is required when using the TravelTime add-in. Looking at the attribute table of the newly created tool results, we see that the five points have an address or street location:
Using the Select by Attribute query tool, we can select the Canary Wharf station in our stations point feature class. This station will serve as our destination in our routing tool. We can now use the TravelTime routing tool and calculate the different routes to Canary Wharf station, displaying the different routes using public transport:
What the transport network analysis shows
Looking at the five different lines (routes) from the different origins to their destination (Canary Wharf station), we see that these intersect with multiple point features from the train/underground point feature layer.
Because the origins are all highly residential areas, we can expect the routes along the different trajectories are likely to get crowded during rush hours in the morning and the evening. In the context of COVID, this means that additional safety measures could be taken to make sure not too many people use public transport for these routes at the same time.
Mapping the routes from highly residential areas to key areas where lots of people work shows where potential bottlenecks can occur and as such is an important transport network analysis tool to map areas where social distancing is crucial.
Additionally, the TravelTime routing tool not only supports current transport networks, but also future ones, for example, the Northern Line Extension in London. This can be used to model the impact of future changes on the transport network and check if these changes remove some of the busy bottlenecks.
In this tutorial, we used the TravelTime plugin to create isochrone maps to identify walking catchment areas for public transport stations in London. This way, we were able to identify and map areas from which no stations could be reached within 30 minutes by foot.
Next, we identified highly residential areas in London to map five public transport routes to Canary Wharf, an area where many people work. This enabled us to see how people move through an urban transport network.
The urban network analysis in GIS from this tutorial can be used to solve potential bottlenecks, for example, identifying areas of the network that are being used the most, plan future infrastructure changes and more.
To create your own analysis, download a free trial of the TravelTime add-in for ArcGIS Pro here.