The PedShed analysis technique has been championed in the Western Australian Liveable Neighbourhood Code as a tool to assess the walkability of a neighbourhood. This tool can be used to assess street layouts for new developments and existing areas, to consider improvements which can be made to connectivity. It can also be used to compare locations for walkability and connectiveness.
The walkable catchment (PedShed) technique
Walkable catchments, sometimes referred to as ‘PedSheds’, are maps showing the actual area within a five minute walking distance from any centre, or ten minutes from any major transport stop, such as a railway station. The centre could be a neighbourhood or town centre. The walkable catchment is simply a technique for comparative evaluation of how easy it is to move through an urban area to get to and from centres or facilities. These maps are the best estimates of walkability.
Walkable catchment calculations are expressed as the actual area within a five minute walking distance and as a percentage of the theoretical area within a five-minute walking distance. The theoretical five minute walking distance is shown as a circle with a radius of about 400 metres drawn around any particular centre. This is an area of 50 hectares. When calculating a ten minute walking distance, the radius used is about 800 metres, resulting in a circle area with an area of 200 hectares. The higher the percentage obtained, the better the walkability and the likely energy efficiency of any urban area. A good target for a walkable catchment is to have 60 per cent of the area within a five minute walking distance, or 10 minutes in the case of railway stations.
Process for calculating walkable catchments
- On a scaled map draw a circle of 400 metre radius around a neighbourhood or town centre, and an 800 metre radius circle around a railway station.
- Starting from the centre, measure along the centre line of all available streets, to a distance of 400 metres.
- Estimate the boundary of the lots within a 400 metre walk, and colour this area. This is the actual area from within which a pedestrian would be able to access a centre along the available streets within a five minute walk.
- In the case of railway stations, complete the task outlined in number 3 above, and complete the task for a ten minute walking distance, using 800 metres as the distance measure. This will provide a map showing the actual distance within a five minute walk, and a ten minute walk from the railway station
- Using a grid of scaled hectares, (that is 100 x 100 metre squares at the appropriate scale), calculate the approximate area in hectares of the area of land coloured in Step 3 above and express this as a percentage of 50 hectares. This identifies the actual area within 400 metres of the centre as a percentage of the 50 hectare circle. In Figure 1, in the example of a conventional subdivision around a neighbourhood centre, the walkable area is 38 per cent, while in Figure 2, for a walkable neighbourhood around a centre and transit station, the walkable area is 60 per cent.
- Repeat the exercise for railway stations, using the hectare grid, and calculate the area accessible within a ten minute walk (800 metres) of the 200 hectare area. In Figure 2 for a walkable neighbourhood the walkable area is 58 per cent. Note that the walkable catchment should always count the area of land used for dwellings but not include public open space contained in the accessible area.
Fine tuning the calculation
There are practical influences on walkable catchments, such as short cuts through parks or along pedestrian paths. These should only be included where there is a high degree of surveillance during evenings and at weekends, from adjoining development that fronts the parks, and where there is good lighting. Similarly, the walkable catchment may need to be reduced where there is poor surveillance and routes are perceived to be unsafe.