6.4. Tire Wear Emission Rate Update#
The tire wear emission rate in zero-emission fleets have been updated to incorporate the impact of their greater weight on PM emissions. Staff reviewed studies that have reported tire wear emissions in both electric vehicles and internal-combustion engine vehicles. On average, tire wear emissions are reported to be 15% higher in electric vehicles compared to their combustion counterparts, based on 40 sets of tests on different vehicles (Beddows and Harrison, 2021, Liu et al., 2021, Timmers and Achten, 2016, Woo et al., 2022). Therefore, LD tire wear generated by zero-emission fleets in EMFAC2025 were adjusted from 8 to 9.2 mg/mi for PM10 and 2 to 2.3 mg/mi for PM2.5 (increased by 15%).
It should be noted that the tire emission rate will be updated in a future version of EMFAC, based on the results of ongoing CARB research projects on non-exhaust emissions (CARB, 2025).