Emission Rates for Light-Duty Truck Towing Operations in Real-World Conditions.

Area of Science:

• Environmental Science
• Automotive Engineering
• Atmospheric Chemistry

Background:

• Light-duty trucks (LDTs) are frequently used for towing trailers.
• Existing research on towing impacts primarily focuses on heavy-duty vehicles, leaving a data gap for LDTs.
• Towing significantly increases engine load, potentially altering exhaust emissions.

Purpose of the Study:

• To quantify in-use exhaust emissions from LDTs during towing operations.
• To compare real-world LDT towing emissions with predictions from the EPA's MOVES model.
• To identify areas for improvement in emissions modeling for LDT towing scenarios.

Main Methods:

• Utilized portable emissions measurement systems (PEMS) to collect real-time data from three common LDTs.
• Characterized emission rates based on operating modes defined in the EPA's MOVES model.
• Compared measured emission rates against MOVES default values.

Main Results:

• Towing operations generally led to increased emissions of CO2, CO, HC, and NOx compared to non-towing operations across most modes.
• Significant increases in CO and HC emissions were observed during higher operating modes while towing.
• Discrepancies between measured emissions and MOVES predictions were noted, particularly at high speeds and high operating modes.
• Individual LDTs exhibited distinct emission profiles even under similar operating conditions.

Conclusions:

• Real-world towing with LDTs results in higher exhaust emissions than typically modeled.
• The EPA's MOVES model requires refinement to accurately predict LDT emissions during towing, especially under demanding conditions.
• Understanding these towing impacts is crucial for accurate air quality assessments and regulatory compliance for LDTs.