The Oregon Department of Transportation (ODOT) undertook an innovative project in 1999 to develop a GIS-based inventory of fish-bearing streams, wetlands, threatened and endangered plant and animal habitat, and other sensitive resource sites within the transportation corridor of state-maintained highways. The objective of this effort was to create an environmental management tool for ODOT’s maintenance and operations activities and to facilitate an exemption under Section 4(d) of the ESA. As a contractor to ODOT, Mason, Bruce & Girard, Inc. (MB&G) has completed this process for four of the five ODOT regions, totaling more than 7,000 miles of state roadway. The project involves the unique integration of high-technology data capture methods, including: (1) high-resolution color infrared digital orthophotography, (2) imagery interpretation and on-screen digitizing of sensitive resource features, (3) road-side verification and capture of sensitive resources using laser rangefinders linked to vehicle-mounted real-time GPS units, and (4) sophisticated GIS modeling. With these tools we are able to accurately determine the locations and attributes of sensitive resources with an error rate of less than five percent. Key project deliverables include: (1) GIS coverages, or data layers, for twelve categories of sensitive resources present along all state roadways, (2) straight-line maps showing locations of sensitive resources for use by ODOT maintenance crews to facilitate resource protection, (3) high-resolution digital imagery of the state-wide transportation corridor (extending 500 feet each side of centerline), and (4) a desktop computer application that allows non-GIS users the ability to access and view these data. The comprehensive spatial database – comprised of the GIS and the digital imagery –allows biological resources to be considered early in the design process for roadway improvement projects, thus facilitating resource protection and environmental permitting. The desktop computer application, GeoBook™ allows environmental scientists, transportation planners, and engineers to query various segments of the state transportation corridor by highway name, number, or milepoint. Functionality includes the ability to pan and zoom in and out so that the user can move through the landscape and view the transportation corridor at any desired scale. The application also allows users to toggle on or off the GIS coverages of the twelve categories of sensitive resources so that they can perform “virtual” environmental project scoping and preliminary alternatives analyses for transportation improvement projects.