Precision and repeatability of the TRAKER vehicle-based paved road dust emission measurement

Testing re-entrained aerosol kinetic emissions from roads (TRAKER), a vehicle based measurement system, has been reported as an alternative to silt measurements for estimating PM10 paved road dust emissions. The precision of the TRAKER system was quantified with repeated measurements over the same roads. A prescribed driving route in Las Vegas, Nevada was traversed with the TRAKER on four consecutive days. The 154 km of paved roads were divided into 645 road segments each representing at least 20 data points and corresponding to links used in the county traffic demand and forecasting model. The TRAKER emission potential, which is related to the emission factor by a multiple of travel speed and provides a measure of a road segment's inherent PM10 dust loading, was averaged over each road segment. Comparing the 4 days of sampling, the coefficient of variation (COV), the standard deviation divided by the average, was <10%, <20%, <50%, and <70% for 126, 402, 619, and 639 of the 645 road segments, respectively. The COV decreased with the speed at the time of measurement from 26% at 5–10 m s−1 to 14% at 25–30 m s−1. No discernible relationships were found between COV and number of data points per road segment, length of road segment, or direction of travel. Over the entire 154 km route, emission potentials on the 4th day were slightly lower than the prior 3 days, owing either to actual changes in road conditions or bias introduced into the measurement by surface wind speed which was highest on the 4th day.