Assessment of the Traffic Enforcement Strategies Impact on Emission Reduction and Air Quality

El-Hansali, Youssef; Farrag, Siham; Yasar, Ansar-Ul-Haque; Malik, Haroon; Shakshuki, Elhadi; Al-Abri, Khalid · 2021 · OpenAlex-citations

DOI: 10.1016/j.procs.2021.03.068

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Summary

This study addresses the complex relationship between traffic enforcement strategies and urban air quality, motivated by the significant health impacts of ambient air pollution and the growing prevalence of traffic congestion in urban areas. While Intelligent Transportation Systems (ITS) are widely adopted to manage traffic, the environmental impact of specific enforcement strategies varies depending on location and conditions. The authors aim to evaluate the potential impact of three typical traffic enforcement strategies—speed limit changes, route changes, and fleet composition changes—on reducing traffic emissions and improving air quality, providing decision-makers with evidence to select optimal strategies for specific contexts. The researchers utilized the EMIT software, a comprehensive tool for compiling and editing emissions inventories, to model and compare emission scenarios. The study established a "Base Case" scenario representing current traffic conditions without restrictions, using data on road attributes, traffic volume, composition, and speed. Three intervention scenarios were then modeled against this baseline: Scenario A1 involved speed restrictions on major roads, reducing speeds to 50 km/h; Scenario A2 implemented a Low Emission Zone (LEZ) by excluding heavy vehicles from a specific area while maintaining total traffic volume; and Scenario A3 also implemented an LEZ excluding heavy vehicles but adjusted for route changes involving only light vehicles. The analysis covered regulated pollutants (NOx, NO2, VOC, CO, CO2, PM10, PM2.5) and unregulated pollutants (Benzene, Butadiene, Methane). The results demonstrate that the impact of these strategies is not uniformly positive across all pollutants. The speed restriction scenario (A1) achieved the highest reduction in Carbon Monoxide (CO) at 25.6%, significantly outperforming the LEZ scenarios, which saw negligible CO reductions (0.48% and 0.25%). However, speed restrictions led to an increase in Nitrogen Oxides (NOx) by 3.51% and Volatile Organic Compounds (VOC) by 18.8%, whereas the LEZ scenarios reduced NOx by up to 49.8% and VOC by up to 28.9%. Regarding particulate matter, the LEZ scenarios were far more effective, reducing PM10 by 61.0% and 68.8% in scenarios A2 and A3, respectively, compared to a modest 10.3% reduction in the speed restriction scenario. Similarly, CO2 emissions were reduced by 45.5% and 56.4% in the LEZ scenarios, while the speed restriction scenario showed a slight increase. The study concludes that traffic enforcement strategies have distinct and sometimes contradictory effects on different pollutants. Speed restrictions are effective for reducing CO but may increase NOx and VOC emissions, likely due to changes in vehicle operating modes. Conversely, fleet composition changes via Low Emission Zones are highly effective for reducing NOx, VOC, PM10, and CO2. These findings imply that policymakers must carefully select strategies based on the specific pollutants they aim to mitigate, as no single strategy optimally reduces all emissions. The authors suggest future research should investigate the long-term impacts of these strategies in the context of emerging technologies like autonomous and hybrid vehicles.

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• speed management