During the 2020 Tokyo Olympic games, the Tokyo Olympic and Paralympic Games Organizing Committee and Tokyo Metropolitan Government are planning to reduce road traffic in central Tokyo to the same level as holidays. Although good air quality has been maintained in Tokyo, this study examined whether further road traffic suppression would improve the air quality. NOx is one of the representative components of automobile exhaust gas. The difference between the NOx concentration on Sundays and weekdays was calculated, and the decrease in NOx concentration due to traffic suppression was estimated. It was found that when the traffic volume in Tokyo was controlled to the same level as holidays, the NOx concentration decreased by about 10-20 ppb near the roadside and by about 5-10 ppb in the residential areas.

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