Permeability of Existing Structures for Wildlife: Developing

A Passage Assessment System (PAS) was developed to help the Washington Department of Transportation (WSDOT) evaluate existing transportation infrastructure for its ability to facilitate terrestrial wildlife movement from one side of a roadway to the other. The outcomes of this research provide mechanisms to allow transportation agencies to identify both opportunities and barriers to wildlife passage along roads. The PAS presented in this report provides an assessment process that differentiates – for different types of wildlife – between structures that are currently functional, those that could be enhanced to become more functional, and those that are not functional for wildlife passage. In this manner, the system enables transportation agencies to prioritize these enhancement opportunities for the greatest cost efficiency and identify location