Urban road traffic scale analysis from the perspective of atmospheric environmental indicators in Tianjin, China

•NOX environmental carrying capacity is a key restriction factor of TAECC of Tianjin.•Classified by the types of vehicles, heavy trucks and large-sized passenger vehicles are the most important restraint factors of TAECC in Tianjin.•A clean vehicles strategy can rapidly improve the TAECC in the short term.•A mobility management strategy can availably improve the TAECC in the long run.

In order to investigate the largest motor vehicle ownership load within the scope of a city with atmospheric environmental indicators as constraint, this article estimates traffic atmospheric environmental capacity (TAEC) and carrying capacity (TAECC) in Tianjin using the A-value method recommended by the Chinese national standard. Our results indicate that NOX carrying capacity is a key restraining factor of TAEC. According to the current vehicle emission levels per year and air quality standard, Tianjin can accommodate 4.21 million vehicles. Classified by the vehicle type, heavy trucks and large-sized passenger cars are identified as the most important restrictive factors of TAECC. Then we analyze change of TAECC and TAECC's service life under the circumstances of clean vehicle strategy and mobility management strategy. Clean vehicles strategy represented by the elimination of heavy-polluting vehicles can reduce emissions of vehicles so that it can rapidly enhance the TAECC in the short term. Mobility management strategy represented by the car purchase restriction, which reduces total motor vehicle travel, is indispensable for improvement of TAECC in the long term. On the whole, the clean vehicles strategy and mobility management strategy should be implemented gradually.

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