This report and the accompanying Guidance Manual summarize the research and resulting guidance developed for achieving surface runoff volume reduction of highway runoff in urban areas. Literature review, synthesis, and focused new analyses were conducted to inform and develop guidance for identifying, evaluating, selecting, and applying volume reduction approaches (VRAs). A stepwise approach was developed and included in the Guidance Manual that guides the user through the evaluation and selection of VRAs. Regulatory and physical considerations were evaluated related to volume reduction in the urban highway environment, and key factors influencing the ability to achieve volume reduction were identified. Recommendations for projectspecific site assessment efforts to support volume reduction planning and design were researched and included. Nine primary VRAs were identified that are specifically applicable to the urban highway environment, as well as accompanying site planning and evaluation approaches. A framework for evaluating the applicability, feasibility, and desirability of these VRAs based on site-specific factors was developed. Processes were also developed for prioritizing VRAs and developing conceptual designs. In support of the Guidance Manual, a spreadsheet based Volume Performance Tool was developed to provide planning level estimates the performance of VRAs, and four white papers on key technical topics were developed. The findings of this research suggest that site-specific conditions are critical in determining the applicability, feasibility, desirability, and effectiveness of VRAs. Additionally, maintaining VRAs is critical for long term effectiveness. (Author/publisher)
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