Activity Centers as described in Imagine Austin are akin to the Multiple Nuclei Model for a city layout created by Chauncy Harris and Edward Ullman in the 1945 article The Nature of Cities. Harris and Ullman argued that cities do not grow a single nucleus but several separate nuclei. Each nucleus acts as a growth point. Because of increased car ownership, people can live in less-dense single-family style neighborhoods near the nuclei containing their job and thus avoid unreasonably long commute time.
Many cities have intentionally or unintentionally developed according to the nuclei model, Houston, in particular, comes to mind. However, while these cities do indeed have multiple growth points and relatively low-density housing, these features have not resulted in the expected reasonable commute times for several reasons.
Most important, typical households today consist of two earners, often in different fields, ie both spouses have different jobs in different locations but live in the same house. Because the two partners will have different jobs in different fields they will likely have to commute to different business centers from the same house. This couple will have to choose which job will be closer to home and likely require the other to have a much longer commute, with all the impacts to quality of life and the environment that follow.
It’s not surprising that Harris and Ullman missed this now obvious fact while writing in 1945 when the idealized and typical household was a single-earner family, ie the husband had a job and the wife stayed home. But that fact should give us pause if we intend to rely on separate job centers to solve our housing shortage and transportation issues. These separate job centers will be unlikely to provide both earners the opportunity to work and live one area and enjoy the access to jobs and amenities like daycare within the short commutes that are necessary for cultivating a successful career and raising a family today. Unfortunately, today that is still most likely to disproportionately impact working mothers.
The activity centers described in Imagine Austin are an important part of our growth plan, but cannot serve as the only or even the essential part of housing and transportation solutions we create in our new land development code. If we really do want to open up opportunities for everyone to grow both a career and a family, we have to ditch the multiple nuclei theory of cities and instead encourage and allow dense concentric development, especially missing middle housing and transitive supportive density close to downtown as the most efficient and environmentally sustainable way for a city to grow.