Vehicle Emission Inventory and Air Quality Impact

Vehicle emission inventories quantify pollutants released by road transport and serve as the foundation for air quality assessment and policy design. Inventories can be constructed via bottom-up methods, which combine real-world activity data and emission factors, or via top-down allocations that disaggregate aggregate fuel consumption. Advances in big-data analytics and near-real-time traffic monitoring have enabled inventories at unprecedented spatial and temporal resolution, revealing hotspots of nitrogen oxides (NOx), particulate matter (PM2.5) and volatile organic compounds. Coupled dispersion and chemical transport models translate these emissions into ambient concentration fields, supporting exposure estimates and the evaluation of control measures. High-resolution approaches have uncovered the role of non-local heavy-duty vehicles, diurnal and seasonal variability in emissions, and the unintended consequences of low-emission zones on upwind communities. Globally, robust inventories underpin strategies to meet air quality standards, inform low-emission vehicle deployment and optimise traffic management. As urbanisation and vehicle fleets expand, integrated inventories and modelling tools remain essential for designing effective mitigation, safeguarding public health and meeting climate targets.

Research from Nature Portfolio

A novel enumeration approach has harnessed billions of truck trajectory records to generate a full-sample, county-level emission inventory. By mapping each vehicle’s movements, this method revealed up to 99 % regional variation in total emissions and up to a 15-fold difference at fine scales compared with aggregated schemes. The study highlighted that aggregated inventories systematically underestimate emissions along major freight corridors and fail to capture the significant share contributed by non-local trucks. Time-allocation proxies derived from daily driving patterns underscored the importance of day-to-day variability, with emission factors varying up to 26-fold. An analysis of low-emission zones demonstrated local reductions but identified emission redistribution to peripheral areas, suggesting that isolated measures must be complemented by comprehensive demand-side and spatially coordinated interventions.

Vehicle Emission Inventory and Air Quality Impact publication trend

The graph below shows the total number of articles in vehicle emission inventory and air quality impact across all publications each year (not limited to Nature Index journals).

Technical terms

Bottom-up methodology: Construction of an emission inventory by summing emissions from individual sources using activity data and emission factors.

Emission factor: A coefficient that relates the quantity of pollutant released to a unit of activity, such as mass per kilometre travelled.

Temporal–spatial resolution: The fineness of time and area grids at which emissions or concentrations are reported.

Dispersion model: A computational tool that simulates the transport and dilution of pollutants in the atmosphere.

Low-emission zone: A designated urban area where vehicles must meet specific emission standards to enter, aimed at reducing local air pollution.

References

1. Development of a vehicle emission inventory with high temporal–spatial resolution based on NRT traffic data and its impact on air pollution in Beijing – Part 1: Development and evaluation of vehicle emission inventory. Atmospheric Chemistry and Physics (2016).
2. High-resolution mapping of vehicle emissions of atmospheric pollutants based on large-scale, real-world traffic datasets. Atmospheric Chemistry and Physics (2019).
3. A big data approach to improving the vehicle emission inventory in China. Nature Communications (2020).
4. Development of a vehicle emission inventory with high temporal–spatial resolution based on NRT traffic data and its impact on air pollution in Beijing – Part 2: Impact of vehicle emission on urban air quality. Atmospheric Chemistry and Physics (2016).
5. On-road vehicle emission inventory and its spatial and temporal distribution in the city of Guayaquil, Ecuador. The Science of The Total Environment (2022).
6. The Potential Impacts of Electric Vehicles on Urban Air Quality in Shanghai City. Sustainability (2021).