This is not a book about construction methods. Rather this is a book about how to accomplish that rarest of feats: Restoring the land occupied by wide, noisy, polluted highways to land usable for parks and buildings. It’s about mending divided communities are mended, mitigating noise and air pollution, and making open space. While rare, these projects are not unprecedented. Moreover, they are becoming increasingly popular, particularly as urban and transit oriented living has seen a resurgence.
The projects over highways are referred to as, among other things, freeway or highway “caps,” “decks,” and “lids.” For convenience, this book will use the term “freeway cap” or just “cap” when referring to these highway airspace projects.
However, these aren’t the only such projects. Some involve reclaiming the space underneath overpasses, or removing the offending highway altogether. Nevertheless, they involve building in a right of way controlled by federal and state departments of transportation, and thus involve many of the same issues.
Accordingly, this is a book about planning, about obtaining public, regulatory, and agency approvals; and about funding projects in highway airspace. “‘Air rights’ or ‘airspace’ are terms used in highway terminology to describe that area above or below the plane of the transportation facility and located within the right-of-way boundaries.” This book will have a special but not exclusive focus on highways that received federal funding when built. These highways have unique process issues and limitations.
My own interest in the topic came from my daily commute into the city, which included crossing over the Interstate 5 trench that separates downtown San Diego from its magnificent Balboa Park. Because it is already in a trench, it seems feasible to cover it and put a park or development on top of it – to essentially make the strip mine of cars disappear. Practically any use would be better than what it is now. I was far from the first to consider this possibility, and the City’s plans already identified capping the freeway as a goal. This project has yet to be realized, but a group of us now regularly meet to give the plan momentum.
Across the country, proponents of plans and projects to build parks and other facilities in highway airspace have expended countless hours researching, planning, lobbying, and fundraising to bring their projects to fruition. Their efforts are fueled by love of community rather than profit. In that spirit, they have been incredibly generous in sharing the lessons and shortening the learning curve for the next project. This book is largely a compilation of their excellent efforts.
 U.S. Dept. of Transportation, Federal Highway Administration, Airspace Guidelines to 23 CFR 710.405 – 710.407 (Revised August 10, 2010)
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