Only 380,000 residents of Australia’s largest cities live in very walkable suburbs, all of them in the inner city. Creating new fringe suburbs with high walkability will be very challenging.

Sydney and Melbourne are by far Australia’s most walkable cities according to US company Walk Score, which released walkability rankings of Australia’s largest cities last week.

Walkability is a term much loved in planning circles. It summarises key urban qualities like density, design and diversity of uses. It extends the simple idea of compactness to also include connectedness and variety of destinations.

Sydney is the clear leader with an overall rating of 63 out of 100, followed by Melbourne with 57 and Adelaide with 53. Canberra’s at the bottom of the pile, with a score of just 40 — that puts it well behind US “sprawl” cities like Phoenix (45), Dallas (47), Houston (50) and Atlanta (53).

Sydney has 29 suburbs defined by Walk Score as a “walker’s paradise” (90 or higher). Melbourne has 12 suburbs that meet the criteria and Brisbane five. Adelaide, Perth, Canberra and Newcastle only have one each.

The algorithm used by Walk Score aggregates the number of amenities within walking distance of a point (eg. an address). The amenities include “businesses, parks, theaters, schools and other common destinations”. More precisely:

“It awards points based on the distance to the closest amenity in each category. If the closest amenity in a category is within 0.25 miles (or 0.4 km), we assign the maximum number of points. The number of points declines as the distance approaches 1 mile (or 1.6 km) — no points are awarded for amenities further than 1 mile.”

It’s important to understand that the scores are approximations. They don’t take account of other factors that influence the desirability of walking in a particular city, like the steepness of hills, climate and crime risk.

Another limitation is the algorithm has no regard for the quality of proximate amenities — it weights them equally. A school is as important as a hardware store and a used car retailer. Further, it uses “as the crow flies” distances, not actual walk distances.

While they shouldn’t be taken too literally, especially at the level of specific addresses, Walk Score’s results are nevertheless consistent with what I would expect at the suburban and city levels.

They show the most walkable suburb in each city is Haymarket (Sydney), Carlton (Melbourne), Northbridge (Perth), Brisbane City, Canberra City, Newcastle City, and Adelaide City.

The average size of suburbs differs significantly between cities, so to get a better comparison I’ve calculated the number of residents who live in suburbs with a score of 90 or more …

In Sydney, 194,885 residents or 5.6% of the metropolitan population live in a “walker’s paradise” and in Melbourne it’s 162,347, or 4.5% of the metro population. The numbers are much smaller in other cities; the next largest is Brisbane with 25,418 (or 1%) living in suburbs with a score of 90 or higher.

Sydney also does better at more modest but still respectable walkability levels; 640,423 Sydneysiders (16.6%) live in suburbs with a score of 80, compared to 386,550 in Melbourne (10.6%) and 98,651 in Brisbane (5.4%). Sydney performs better at the bottom end too — 80,961 residents live in suburbs with a Walk Score of less than 30, compared to 146,526 in Melbourne and 183,579 in Brisbane.

Taken together, the suburbs with 90-plus walk scores in Australian cities house just 380,219 residents. They’re all located in the inner city, most of them close to the CBD. That has important implications for the policy objective of enhancing walkability across metropolitan areas.