Impact of asphalt rubber friction course overlays on tire wear emissions and air quality models for Phoenix, Arizona, Airshed

Tire wear contributes to atmospheric particulate matter (PM) and is regulated by the U.S. Environmental Protection Agency because PM has been shown to affect human health. Vehicle emissions are a significant source of both PM2.5 and PM10. Vehicle fleet emissions per mile traveled have been reduced significantly in the past 30 years as a result of improved engine operation and tailpipe controls. However, "zero emission" vehicles will continue to generate PM from tire wear, road wear, brake wear, and resuspended road dust. In this study, aerosol measurement techniques at Arizona State University were applied to evaluate tire wear emissions from the vehicle fleet by using the Deck Park Tunnel in Phoenix, Arizona. The Deck Park Tunnel highway surface was portland cement concrete (PCC) and was resurfaced with an asphalt rubber friction course (ARFC) layer as part of the Arizona Department of Transportation Quiet Pavements Program. This study took advantage of a rare opportunity to sample tire wear emissions at the tunnel before and after the ARFC overlay. The hypothesis was that an ARFC surface results in less tire wear than the existing PCC road surface. This paper reports on the measured PM emissions from the on-road vehicle traffic during typical highway driving conditions for the two different roadway surfaces. It presents the analysis of representative tire tread samples for tire wear marker compounds and a comparison of roughness and frictional surface characteristics as measured before and after the ARFC overlay. The study found that emission rates of tire wear per kilometer driven on PCC road surfaces were 1.4 to 2 times higher than emission rates of tire wear on ARFC road surfaces.