Will the 15-minute city cause the US suburbs to disappear? 6/7

Featured image

Urbanisation in the US is undergoing major changes. The image of a central city surrounded by sprawling suburbs therefore needs to be updated. The question is what place does the 15-minute city have in it? That is what this somewhat longer post is about
From the 1950s, residents of US cities began moving en masse to the suburbs. A detached house in the green came within reach for the middle and upper classes, and the car made it possible to commute daily to factories and offices. These were initially still located in and around the cities. The government stimulated this development by investing billions in the road network.
From the 1980s, offices also started to move away from the big cities. They moved to attractive locations, often near motorway junctions. Sometimes large shopping and entertainment centres also settled there, and flats were built on a small scale for supporting staff. Garreau called such cities 'edge cities'.
Investors built new suburbs called 'urban villages' in the vicinity of the new office locations, significantly reducing the distance to the offices. This did not reduce congestion on congested highways.
However, more and more younger workers had no desire to live in suburbs. The progressive board of Arlington, near Washington DC, took the decision in the 1980s to develop a total of seven walkable, inclusive, attractive and densely built-up cores in circles of up to 800 metres around metro stations. In each was a wide range of employment, flats, shops and other amenities . In the process, the Rosslyn-Balston Corridor emerged and experienced rapid growth. The population of the seven cores now stands at 71,000 out of a total of 136,000 jobs. 36% of all residents use the metro or bus for commuting, which is unprecedentedly high for the US. The Rosslyn-Balston Corridor is a model for many other medium-sized cities in the US, such as New Rochelle near new York.
Moreover, to meet the desire to live within walking distance of all daily amenities, there is a strong movement to also regenerate the suburbs themselves. This is done by building new centres in the suburbs and densifying part of the suburbs.
The new centres have a wide range of flats, shopping facilities, restaurants and entertainment centres.  Dublin Bridge Park, 30 minutes from Columbus (Ohio) is one of many examples.
It is a walkable residential and commercial area and an easily accessible centre for residents from the surrounding suburbs. It is located on the site of a former mall.
Densification of the suburbs is necessary because of the high demand for (affordable) housing, but also to create sufficient support for the new centres.
Space is plentiful. In the suburbs, there are thousands of (semi-)detached houses that are too large for the mostly older couples who occupy them. An obvious solution is to split the houses, make them energy-positive and turn them into two or three starter homes. There are many examples how this can be done in a way that does not affect the identity of the suburbs (image).
New construction in suburbs
This kind of solution is difficult to realise because the municipal authorities concerned are bound by decades-old zoning plans, which prescribe in detail what can be built somewhere. Some of the residents fiercely oppose changing the laws. Especially in California, the NIMBYs (not in my backyard) and the YIMBYs (yes in my backyard) have a stranglehold on each other and housing construction is completely stalled.
But even without changing zoning laws, there are incremental changes.  Here and there, for instance, garages, usually intended for two or three cars, are being converted into 'assessor flats' for grandma and grandpa or for children who cannot buy a house of their own.  But garden houses are also being added and souterrains constructed. Along the path of gradualness, this adds thousands of housing units, without causing much fuss.
It is also worth noting that small, sometimes sleepy towns seem to be at the beginning of a period of boom.  They are particularly popular with millennials. These towns are eminently 'walkable' , the houses are not expensive and there is a wide range of amenities. The distance to the city is long, but you can work well from home and that is increasingly the pattern. The pandemic and the homeworking it has initiated has greatly increased the popularity of this kind of residential location.
All in all, urbanisation in the US can be typified by the creation of giant metropolitan areas, across old municipal boundaries. These areas are a conglomeration of new cities, rivalling the old mostly shrinking and poverty-stricken cities in terms of amenities, and where much of employment is in offices and laboratories. In between are the suburbs, with a growing variety of housing. The aim is to create higher densities around railway stations. Besides the older suburbs, 'urban villages' have emerged in attractive locations. More and more suburbs are getting their own walkable centres, with a wide range of flats and facilities. Green space has been severely restricted by these developments.
According to Christopher Leinberger, professor of real estate and urban analysis at George Washington University, there is no doubt that in the US, walkable, attractive cores with a mixed population and a varied housing supply following the example of the Rosslyn-Ballston corridor are the future. In addition, walkable car-free neighbourhoods, with attractive housing and ample amenities are in high demand in the US. Some of the 'urban villages' are developing as such.  The objection is that these are 'walkable islands', rising in an environment that is anything but walkable. So residents always have one or two cars in the car park for when they leave the neighbourhood, as good metro or train connections are scarce. Nor are these kinds of neighbourhoods paragons of a mixed population; rents tend to be well above the already unaffordable average.
The answer of the question in the header therefore is: locally and slowly