Planning with WebCAT

NOTE: A problem in WebCAT means PDF and PNG output files cannot incorporate and display the current mapping window. Our technical team is working on this. We're sorry for the inconvenience.

What is WebCAT?

WebCAT is a toolkit to help the work of professional planners in London. WebCAT stands for Web-based Connectivity Assessment Toolkit. The toolkit currently contains two main tools: PTAL and Time Mapping (TIM).

WebCAT allows users to create their own PTAL maps and view PTAL for future scenarios. PTAL values are now pre-calculated using a grid of points at 100m intervals across the Greater London area.

Connectivity assessment guide

Our complete guide to connectivity assessment will help WebCAT users become familiar with the techniques we use to assess levels of connectivity in London.

The guide explains how PTAL and TIM are calculated.


Terms used in WebCAT are explained in our WebCAT glossary.

WebCAT features


PTAL is a measure of connectivity. A high PTAL in a specific location indicates good connectivity to the public transport network. PTAL values are influenced by the walking distance to nearby stations and stops, and by the frequency of services at these stations and stops.

The TIM feature of WebCAT allows users to design maps showing how long it takes to travel to or from a selected location.

PTAL and TIM are approximated. They represent the best estimate of connectivity based on the information available to us at the time of calculation. Information about future connectivity is difficult to calculate accurately. Users should consider this uncertainty when using outputs from WebCAT.

PTAL spreadsheet macro

If you feel that a WebCAT-calculated PTAL is not representative of your chosen site (for example, it's on the boundary of two cells giving different levels), please ask for a copy of our PTAL spreadsheet macro and guide by sending an email to

This macro can convert the PTAL calculation text report to a spreadsheet format for you to modify accordingly.

WebCAT scenarios

WebCAT is used when planning new houses or other developments in London. In the planning process it's important to know whether the level of connectivity around the development area is expected to change. The future scenarios in WebCAT will allow you to check this. Please note that information about future service is indicative and subject to uncertainty.

Connectivity and accessibility

We use the term 'connectivity' to describe the quality of the transport connections between different places in London. We no longer use the term 'accessibility' to do this because it's also used when referring to step-free travel.

PTAL in the planning process

Every process or analysis where PTAL was used should still use it. Users may want to also use the TIM tool on WebCAT but there is no such formal requirement to do so.

WebCAT and TfL Journey Planner

WebCAT is not designed to reflect real-time travel conditions. It provides a consistent baseline for planning processes. Changes to London's transport system will be updated in WebCAT periodically. TfL's Journey Planner is more suitable tool for those interested in current travel time information.

WebCAT is not the right tool for planning your journey. It is meant to be used by professional planners in London Boroughs, Greater London Authority officers, consultants and so on.

New planning scenarios

We will occasionally add new planning scenarios to WebCAT if the information relevant to a new scenario becomes available. If you're interested in a planning scenario which is not currently included in WebCAT, please contact us.

Measures of connectivity

We still use the CAPITAL measure of connectivity, and occasionally ATOS, but they're not available on WebCAT.

See the Connectivity guide above for details about the different measures we use.

Using WebCAT

See the formal WebCAT terms of use. Users will also need to agree to the Google terms of service.

Search for a specific location

You can enter an address, postcode or map coordinates (Easting and Northing) in the search line on the top left side of the screen. The map will automatically zoom into the selected location, or present several options if the search may refer to several different places. You can also click on a different location on the map to move to that location.

Navigate around the map

When a pointing hand icon is shown, you can hold the mouse down and pan across the window to select a new location. To select a new location, click the pointer anywhere on the map. You can also use the 4 navigation buttons to pan across the map.

Change the current display

Once you have made a selection on the map, you can toggle between the PTAL and TIM using the PTAL and TIM buttons.

You can choose any of the drop-down menus, shown under the map key, to change the data which is displayed. If you make new choices from the drop-down menus, click the 'update' button below these menus in order to update the presentation.

You can zoom in and out, up to a certain limit. The map key will explain the colours used in the map.

Information presented by default

The default presentation is PTAL for the base year (2011) for the whole of Greater London.

If you chose TIM but have not yet selected a location, a black-and-white map is displayed. The default TIM output is for the base year (2011) in the morning peak using all public transport modes.

Add layers to the map

Click on the menu icon to display additional mapping layers to give context to PTAL and TIM displays. The additional layers available include the boundaries between London Boroughs, London Wards, 'output areas' and 'lower super output areas' from the 2011 census.

Other layers present stations, stops and piers. Layers of Opportunity Areas and Areas for Intensification, as defined in the London Plan, can be displayed as well. You can also select Google Maps or Google Aerial Photography as the background mapping.

Direction menu

TIM outputs can be created based on either travel times from the place you selected to all other places, or travel times from all places to the place you selected, or the average of the two. The average is the default.

WebCAT will be regularly updated with new features. Keep up with the latest developments on the WebCAT updates page.


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