Storm-water runoff from highway pavement is capable of mobilizing and transporting a wide gradation of particulates and solids. A significant fraction of this particulate matter is generated from traffic activities, including the abrasion between tires and pavement. Particulate accumulation and characteristics from an urban Interstate pavement site are investigated. The southbound asphalt pavement section studied consisted of four traveled lanes and two paved shoulders with a measured average daily traffic of 110,000. The pavement section has a transverse slope of 0.020 m/m and a longitudinal slope of 0.004 m/m. Recovery of deposited particulate matter indicates that accumulation of particulate matter along the east paved shoulder (the downslope shoulder) is significantly greater than that along the the west paved shoulder (the upslope shoulder) or the pavement. Particles larger than 25 μm were separated mechanically to generate particle size distributions (PSDs) and also to separate particles for further analysis. The east shoulder PSDs were consistently coarser across the entire size gradation than the west shoulder and pavement PSDs. Particle specific gravity ranged from 2.70 to 3.01 g/cm³ across all gradations. Particle specific surface area increased with decreasing particle size for all gradations. In contrast, total particle surface area decreased with decreasing particle size. Integration of metal element concentration (in micrograms per gram) of zinc, copper, cadmium, and lead with the mass fraction of each particle size demonstrates that most of the metal mass is associated with the coarse to mid-range-size particles. Study results are useful for design of roadway drainage appurtenances and water quality control devices that clarify storm water mainly through the separation of particles.