- The purpose of this project is to modify the Transportation Options Health Impact Estimator (TO Estimator) tool to quantify the health impacts of outdoor recreation in Oregon. The TO Estimator tool uses the Integrated Transportation and Health Impact Model (ITHIM) to quantitatively estimate the hypothetical health impacts of transportation mode shifts through changes to physical activity, air pollution, and injuries. The changes in physical activity are measured by shifts in active transportation like walking and cycling. The recreation modified version of the tool, Outdoor Recreation Health Impact Estimator (OR Estimator), increases the number of activities that can be measured to include 31 different outdoor recreation activities. Participation data from Oregon’s Statewide Comprehensive Outdoor Recreation Plan (SCORP) survey is also incorporated in the tool to create a baseline for comparison. This report demonstrates how the tool might be used in Coos County, Oregon looking at changes in trail walking participation. An increase in trail walking from an average of 34.5 minutes/week to 150 minutes/week was estimated to reduce illness related costs by up to $5.3 million annually. The OR Estimator will enhance discussions about outdoor recreation management in Oregon. In addition, it will provide a tool that can be used by outdoor recreation managers and planners to articulate the impact recreation has on their communities, and use this information in recreation and community plans, grant applications, and project prioritization.