Carlos Moreno, a professor at the Sorbonne University, helped Mayor Anne Hidalgo develop the idea of the 15-minute city. He said that six things made people happy: living, working, amenities, education, wellbeing, and recreation. The quality of the urban environment is enhanced when these functions are realized near each other. The monofunctional expansion of cities in the US, but also in the bidonvilles of Paris, is a thorn in his side, partly because this justifies owning a car.
A more precise definition of the concept of the 15-minute city is needed before it can be implemented on a large scale. It is important to clarify which means of transport must be available to reach certain facilities in a given number of minutes. The list of facilities is usually very comprehensive, while the list of means of transport is usually only vaguely defined. But the distance you can travel in 15 minutes depends on the availability of certain modes of transport (see figure above).
Advocates of "new urbanism" have developed the tools to design 15-minute cities. They are based on three zones: the 5-minute walking zone, the 15-minute walking zone, which coincides with the 5-minute cycling zone, and finally the 15-minute cycling zone. These are not static concepts: In practice, the zones overlap and complement each other.
The 5-minute walking zone
This zone corresponds to the way in which most residential neighbourhoods functioned up until the 1960s, wherever you are in the world. Imagine a space with an average distance from the center to the edge of about 400 meters. In the center you will find a limited number of shops, a (small) supermarket, one or more cafes and a restaurant. The number of residents will vary between two and three thousand. Density will decrease from the centre and the main streets outwards. Green spaces, including a small neighbourhood park, will be distributed throughout the neighbourhood, as will workshops and offices.
In the case of new construction, it is essential that pedestrian areas have a dense network of paths without crossings at ground level with streets where car traffic is allowed. Some paths are wider and allow cycling within the 5- and 15-minute cycle zones. The streets provide access to concentrated parking facilities.
The 5-minute cycle zone and the 15-minute walking zone.
Here the distance from the center to the edge is about one kilometer. In this area, most of the facilities that residents need is available and can be distributed around the centers of the 5-minute walking zones. For example, a slightly larger supermarket may be located between two 5-minute walking zones. This zone will also contain one or more larger parks and some larger concentrations of employment.
This zone can be a large district of a city, but it can also be a small municipality or district of around 15 to 25,000 inhabitants. With such a population there will be little room for dogmatic design, especially when it comes to existing buildings. But even then, it is possible to separate traffic types by keeping cars off many streets and clustering car parks. The bottom line is that all destinations in this zone can be reached quickly by walking and cycling, and that car routes can be crossed safely.
The car will be used (occasionally) for several destinations. For example, for large shopping trips to the supermarket.
The 15-minute cycle zone.
This zone will be home to 100.00 or more residents. The large variation is due to the (accidental) presence of facilities for a larger catchment area, such as an industrial estate, a furniture boulevard or an IKEA, a university or a (regional) hospital. It is certainly not a sum of comparable 5-minute cycle zones. Nevertheless, the aim is to distribute functions over the whole area on as small a scale as possible. In practice, this zone is also crossed by several roads for car traffic. The network of cycle paths provides the most direct links between the 5-minute cycle zones and the wider area.
The main urban development objectives for this zone are good accessibility to urban facilities by public transport from all neighbourhoods, the prohibition of hypermarkets and a certain distribution of central functions throughout the area: Residents should be able to go out and have fun in a few places and not just in a central part of the city.
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