Cities Benefitting From Decking Highways With Parks

As urban auto impacts become less welcome, highway decks have moved from the novel to the expected. Despite the sometimes considerable cost - as much as $500 per square foot - they are no longer classified as porkbarrel. They've been redefined as amenity investment with high economic payback.

It wasn't until the 1970s construction of Seattle's Freeway Park atop a downtown section of Interstate 5 that the "deck-the-freeway" concept began getting serious attention - opening as it did in time for the Bicentennial. Since then, there have been many more deckings. Phoenix, for instance, put 10-acre Hance Park over the Papago Freeway, uniting uptown and downtown and providing open space adjacent to the city's central library, while Duluth, Minnesota, put in place three different deck parks over Interstate 35 to bridge the divide the road created between the city and the Lake Superior waterfront. More recently, New Jersey placed innovative freeway parks in Trenton and Atlantic City.

A study carried out by the Trust for Public Land's Center for City Park Excellence found that the average size of freeway parks in the U.S. is about nine acres, and that, on average, each one covers 1,620 linear feet of highway.

While construction costs for deck parks can be wincingly high, there is also an upside: The land itself is generally free, made available as air rights by state transportation agencies. In center-city locations, this can amount to a multimillion-dollar gift. Land near the Santa Ana Freeway by Los Angeles City Hall, for instance, goes for between $2 million and $3 million an acre. In near-downtown San Diego by Balboa Park, an acre is worth up to $13 million.