Urban fabrics: walking, transit and car

The theory of urban fabrics demonstrates how different types of cities are combinations of walking, transit and car fabrics, based on their transport systems and the universal travel time budget.

The distances and/or transport speeds that generate these urban fabrics and their associated elements, functions and qualities are described below in contrast to the 15-minute city. Tasks of statutory planning and transport planning are different for each of the three urban fabrics.

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© Chamberlain (2022)

The 15-minute city

The 15-minute city proposes that city planning should be informed by the premise that residents can undertake all their daily routines within a maximum 15-minute walk, bicycle or public transport journey.

Urban fabrics and the Marchetti constant

The theory of urban fabrics takes the longest daily journey, typically the journey to work, as its starting point. This journey has typically averaged 30 minutes (one way) throughout urban history, a measure also known as the ‘Marchetti constant,’ after the researcher who popularised the concept in the 1990s.

As transport technology evolved and the speed and spread of movement increased in urban areas, the Marchetti constant allowed:

• for the walking city, at 5 km/h speed, to spread to a maximum radius of 2.5 km
• for the inner transit city of trams and buses, at 12-15 km/h speed, to spread to a maximum radius of 6-8 km (from the 19th century onwards)
• for the outer transit city of metros and suburban railways, at 30-40 km/h speed, to penetrate up to 15-20 km into the urban hinterland, but only along the rail corridors
• for the transit city to expand further into the automobile city, making the entire 20-30 km radius accessible within half an hour if traffic flows freely (in the 20th century).

The walking, transit and automobile city

In most contemporary cities, elements of the walking city, the transit city and the automobile city continue to overlap.

Typically, the walking city has a fine grain, medium to high densities and a high level of land use diversity, allowing people to access many different activities at walking speed.

The transit city is also characterised by high densities – facilitating walking at the local scale – but a local mix of land uses becomes less important as public transport can provide the links between residential areas, employment centres, commercial and entertainment areas.

In the automobile city this specialisation of land uses increases further, but at much lower densities often rendering the urban fabric unsuitable or dysfunctional for pedestrians beyond some recreational walking at neighbourhood level.

Table: Key characteristics of the three urban fabrics.

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Source: Summarised from Newman et al, 2016, pp 447-450

The 15-minute city as the walking city

In this context, the 15-minute city is an attempt to strengthen walking city characteristics throughout the contemporary, mixed urban fabric. Apart from achieving proximity, density and diversity of a level that makes walking and cycling the primary choice of travel, it is critical that 15-minute city qualities become ubiquitous rather than being confined to selected areas. These qualities should inform the evolution of neighbourhoods across all metropolitan areas.

This is where a tight connection between urban growth and public transport networks, the TOD template, provides a useful principle of spatial order.

Further resources

If you would like to explore some of the concepts we have covered in more detail, the following resources are optional.

The surprising stickiness of the ‘15-minute city’

Introducing the 15-minute city project. Putting people at the centre of urban transformation

Anthropological invariants in travel behaviour

Introducing the 15-minute city: Sustainability, resilience and place identity in future post-pandemic cities

Theory of urban fabrics: Planning the walking, transit/public transport and automobile/motor car cities for reduced car dependency