WSDOT chip seals : optimal timing, design and construction considerations.

The Washington State Department of Transportation (WSDOT) does not have sufficient pavement preservation funding to keep up with inflation and pavement needs. This has caused WSDOT to emphasize in its preservation program lower-cost options such as chip seals. The study was conducted on several aspects of WSDOT chip seals including (1) the optimum timing for alternating chip seals (or Bituminous Surface Treatments (BSTs)) with hot mix asphalt (HMA) overlays, (2) design of chip seal application rates, and (3) a range of construction and performance factors. The research incorporated surveys, literature reviews, and five BST meetings that were held between 2006 and 2011. All of these activities are summarized in this report. WSDOT has continuously changed both policy and specifications as new information became available for improving their chip seal performance. In recent years, a policy change resulted in using chip seals on roadways with up to 10,000 annual daily traffic (ADT). As such, a secondary factor examined in this study was maximum ADT levels which provide for sensible chip seal construction.