To what extent the traffic restriction policies can improve its air quality? An inspiration from COVID-19.

In hazy days, several local authorities always implemented the strict traffic-restriction measures to improve the air quality. However, owing to lack of data, the quantitative relationships between them are still not clear. Coincidentally, traffic restriction measures during the COVID-19 pandemic provided an experimental setup for revealing such relationships. Hence, the changes in air quality in response to traffic restrictions during COVID-19 in Spain and United States was explored in this study. In contrast to pre-lockdown, the private traffic volume as well as public traffic during the lockdown period decreased within a range of 60-90%. The NO2 concentration decreased by approximately 50%, while O3 concentration increased by approximately 40%. Additionally, changes in air quality in response to traffic reduction were explored to reveal the contribution of transportation to air pollution. As the traffic volume decreased linearly, NO2 concentration decreased exponentially, whereas O3 concentration increased exponentially. Air pollutants did not change evidently until the traffic volume was reduced by less than 40%. The recovery process of the traffic volume and air pollutants during the post-lockdown period was also explored. The traffic volume was confirmed to return to background levels within four months, but air pollutants were found to recover randomly. This study highlights the exponential impact of traffic volume on air quality changes, which is of great significance to air pollution control in terms of traffic restriction policy. Supplementary Information: The online version contains supplementary material available at 10.1007/s00477-022-02351-7.

New local design in the new normal: Sustainable city for outbreak risk

There is an urgent need to transform the conventional city into a flexible and sustainable city that can respond to the risks of outbreaks in a broad sense, including global infectious disease pandemics and large-scale disasters. However, today's cities have many trade-off (compatibility) problems related to peacetime-emergency, global-local, and so on, in addition to inertia to change. In this paper, we presented the idea of a new local design in which people's well-being is maintained and improved even in the new normal, based on the idea of “three compatibility problems.” As a concrete measure, we developed the concept of milieu that emphasizes local “place” and “innovation,” and expresses its socio-economic function after including the void spaces of today's cities. At the same time, we proposed an autonomous and self-sustaining segmented city that can respond to outbreaks by increasing the self-efficacy of citizens. Furthermore, based on an analysis of the implementation cases of integrated transportation machizukuri with railway development in Japan, we reported that the emergence of new local design has already been seen in industry-government-private partnership efforts.