Comparison of Road-Side Emissions Measurements from Heavy-Duty Diesel Vehicles to MOVES5

This study compares MOVES5 emissions estimates for nitrogen oxides (NO, NO2, and NOx), ammonia (NH3), and carbon monoxide (CO) to individual roadside emission measurements from heavy-duty (HD) diesel vehicles. Vehicle measurements were collected in Perry, Utah (winter 2020 and summer 2023) and Peralta, California (spring 2017), using the Fuel Efficiency Automobile Test (FEAT) remote sensing device. MOVES5 underestimated NOx in the Utah winter campaign. MOVES5 underestimated mean NO emissions and overestimated mean NO2 emissions across all campaigns, indicating potential deficiencies in the NO/NOx and NO2/NOx ratios used by the model. NH3 estimates were significantly higher than measurements, while CO estimates closely matched real-world measurements. Analysis by model year found that MOVES5 consistently underestimated emissions of the older model years and overestimated emissions from the newest model years for most pollutants. In the Utah winter campaign, MOVES5 underestimated NOx by 47%, which, when applied to Utah’s emission inventory, suggests that HD diesel vehicles may contribute an additional ~1300 tons/year of unaccounted NOx. Using a broader range of real-world measurements to update the MOVES model could improve its accuracy in estimating HD diesel vehicle emissions.