Urban road network design for alleviating residential exposure to traffic pollutants : Super-block or Mini-block?

This study addresses the knowledge gap between urban road network design and residents’ exposure to traffic pollutants. Computational fluid dynamics (CFD) simulations are employed to evaluate three representative design strategies: (1) Mini-block with 1-lane roads in high density; (2) Regular-block with 2-lane roads in median density; and (3) Super-block with 4-lane roads in low density. Daily activities of different age groups are considered to examine the vulnerable population, using the personal intake fraction (PI_g, ppm) that represents the emitted pollutant inhaled averagely by each resident. By changing from Super-block to Mini-block, the outdoor PI_g decreases for the young and adult groups, but remains largely unchanged for the elderly group. The indoor PI_g is given for individual building levels. The Mini-block leads to a relatively uniform distribution of indoor PI_g and the value goes up to 0.251 ppm for the elderly group. For the Regular-block and Super-block, residents living in buildings with a long roadside façade tend to bear an unequal level of pollutant burden. With the Super-block, elderly residents in 25% of the buildings have an high indoor PI_g with the maximum value of 0.554 ppm, nearly four times larger than that of 0.121 ppm in buildings not close to the roads. The results can serve as a basis for supporting the new design and urban redevelopment to improve neighborhood liveability.

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