Spatial applicability of emission factors for modeling mobile emissions

Area of Science:

• Environmental Science
• Transportation Engineering
• Atmospheric Chemistry

Background:

• Mobile emission factors are crucial for estimating emissions and setting vehicle standards.
• Current methods rely on driving cycles to determine these factors.
• The spatial representativeness of these driving cycles is not well understood.

Purpose of the Study:

• To assess the spatial representativeness of driving cycles used for California's mobile emission inventories.
• To determine the accuracy of emission rates derived from standard driving cycles across different urban environments.

Main Methods:

• Conducted 214 dynamometer tests on 16 vehicles using six different driving cycles.
• Utilized a random effects analysis of variance to analyze emission rate differences.
• Compared emission data from various city-specific driving cycles.

Main Results:

• Significant differences in emission rates (CO, THC, NOx) were observed across different driving cycles.
• Emission factors based on standard Los Angeles driving cycles may lead to inventory inaccuracies.
• Potential overestimation or underestimation of mobile source pollutants by up to 30% in certain regions.

Conclusions:

• Standard driving cycles may not accurately reflect real-world driving conditions in all Californian regions.
• Regional variations in traffic congestion and roadway networks significantly impact mobile source emissions.
• Mobile emission inventories require more spatially representative driving cycles for improved accuracy.