Measuring the 20-minute Neighbourhood

The 20-Minute Neighbourhood Concept

The concept of the 20-minute neighbourhood has been adopted as an urban planning principle by all levels of government throughout Australia. Simply stated, the 20 minute neighbourhood can be defined as “the ability to meet your everyday, non-work needs locally, primarily within a 20-minute walk” (Plan Victoria: 2017-2050).

As part of a broader project around measuring urban liveability, we at propella.ai have implemented software that can provide urban planners and urban policy makers with a rapid assessment of the walkability of any neighbourhood anywhere in Australia – within seconds. We have also developed the capability to measure and compare liveability and social infrastructure metrics within these walkable neighbourhoods (some of which are outlined in this article, https://www.propella.ai/post/social-infrastructure-planning-for-the-20-minute-neighbourhood)

Providing standard comparative metrics around walkability is a four-stage process:

1. Identify the subject location around which you wish to measure walkability;
2. Derive the 20-minute theoretical walkable area around your location;
3. Derive the 20-minute actual walkable area around your location;
4. Calculate the ratio between the theoretical and the actual walkable areas (what we term 'NWR' - Neighbourhood Walkability Ratio). This is a standard comparable metric of walkability.

1)  The location

The location around which walkability is measured is always a geo-spatial point on a two-dimensional map. We can identify this location by entering a longitude and latitude, or alternatively with a simple click of the mouse. This location is identified in Figures 1 to 3 as a blue location marker.

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Caption - Figure 1: Walkability of Kensington - an inner northern suburbs of Melbourne

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2)  Theoretical walkable area

The theoretical walkable area is defined by a circle, the radius of which centres on the subject location. When we calculate the theoretical walkable area, we assume the surface of this area to be flat, with absolutely no impediments to walking any direction in a straight-line – like walking across a flat desert. There are accepted distances that correspond to average theoretical walking times from a subject location. For a 20-minute walk time, the radius of the circle is 1.6 km (the area of which is 8.042 square kilometres), while for a 40-minute walk time the radius is 3.2 km (the area of which is 32.17 square kilometres) [i]. In Figures 1 to 3, all theoretical 20-minute walking areas are bounded by the inner circle, while the theoretical 40-minute walking area is bounded by the outer circle.

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Caption - Figure 2: Walkability of Ringwood - an outer north-eastern suburb of Melbourne

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3)  Actual walkable area

The actual walkable area can be identified by an isochrone map (sometimes referred to as a 'PedShed'). Like the theoretical circle, an isochrone map is centred on a specific location. Unlike the theoretical circle, the isochrone map considers the impact of transit paths like roads and walking paths, and other infrastructure that shortens the time it takes to walk a specific distance away from the centre. In Figures 1 to 3, the 20-minute (1.6 km) actual walkable area (isochrone) is shown in yellow. The 40-minute actual walkable area (isochrone) is shown in blue. In urban environments, the actual walkable area (as defined by the isochrone) is always smaller than the theoretical walkable area (as defined by the circle).  

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Caption - Figure 3: Walkability of Craigieburn - an outer northern suburb of Melbourne

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4)  Neighbourhood Walkability Ratio (NWR)

Using both theoretical and actual walking distances, we can calculate a measure that allows us to compare walkability across two or more locations – we call this measure the “Neighbourhood Walkability Ratio” or NWR.

The idea of the NWR is very simple. It is the ratio of the actual walking area to the theoretical walking area, and can be calculated in the following manner:

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The concept of the NWR is intuitively quite simple. It is the percentage of the theoretical walking area covered by the actual walking area. The higher this percentage, the more walkable the location. The generally accepted position (by Plan Victoria and other authorities) is that a good walkable neighbourhood has an NWR of 0.6 or above. Table 1 below compares the 20-minute and 40-minute NWRs for the Melbourne suburbs of Kensington, Ringwood and Craigieburn:

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Caption - Table 1: Neighbourhood walkability ratios for four Melbourne locations

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Measuring the walkability of Greater Melbourne

We conducted some analysis to understand how walkability varied across Greater Melbourne. Taking over 5,200 randomly sampled residential parcels (properties), we calculated the associated NWR for each location. The resulting NWR heatmap is showed below in Figure 4. The darker points represent greater walkability. Inner urban areas tend to have better NWR ratings (although not all), and, as expected, as we travel further out towards regional areas, walkability values decrease (except around key activity centres).

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Caption - Figure 4: the NWR heatmap for Greater Melbourne (n = 5,283 locations)

Analysis of the distribution of NWR values for all 5,283 sample locations indicates a median value of 0.42(far below the aspirational target of 0.60), an inter-quartile range of 0.31 - 0.52, and NWR values peaking at about 0.71 and dropping to as low as 0.01.

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Caption - Figure 5: Boxplot of NWR results for Greater Melbourne sampling

So what is one of Melbourne's most walkable locations? Rathdowne Street in Carlton, with an NWR of 0.713.

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Caption - Figure 6: 49 Rathdowne St, Carlton - NWR: 0.713

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And some of the lowest ranked walkable locations were in Donnybrook, Kangaroo Ground and Mount Cottrell...

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Caption - Figure 7: Residential locations with NWR less than 0.014

propella.ai and Liveability metrics

propella.ai is a geospatial analytics company that specialises in providing solutions for complex locational problems. As part of our research, we have taken on the task of automating the measurements associated with liveability – of which the 20-minute walkable neighbourhood is central.

As part of propella.ai’s development of automated liveability measurements, we have created easy to use and interpret solutions for estimating walkability. Specifically, we can map, calculate and compare walkability around ANY location within Australia – whether it be a retail or commercial precinct, a railway station, an individual house, a vacant lot, or indeed any urban environment. We are particularly excited about having developed a methodology to provide walkability distributions for large cities such as Melbourne, Sydney or Brisbane. We can also provide similar distributions for smaller cities such as Goulburn, Ballarat, Launceston or Townsville.

Learn more about Melbourne's Most "Liveable" Suburbs

We have partnered with CoreLogic's "Onthehouse" platform, to determine Melbourne's most liveable suburbs!  You can read about that project here @ propella.ai/blog/new-liveability-rating-score-designed-to-provide-consumers-with-insights-where-to-buy-and-invest

You can also read more about how we devise liveability scores using "walkability" in our blog "Assessing Liveability Though Walkable Neighbourhoods" @ propella.ai/blog/assessing-liveability-through-walkable-neighbourhoods

For more information, contact us here, www.propella.ai/contact

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