To investigate the effect of aggregate type on pavement friction, researchers used Texas as a test model and constructed 59 seal coat test sections 1,000 feet (304 m) long in the four climatic regions of the state. The environmental characteristics of these four regions included: wet and no freeze; wet and freeze-thaw cycling; dry and no freeze; and dry and freeze-thaw cycling. Researchers used many of the aggregate types that are common to each region, and economically available, in the design mixture for each seal coat section.