Underutilized spaces present the chance to reconnect neighborhoods, offer new transportation options and encourage physical activity.

We’ve all seen those online interactive tools that allow you to scroll from one side of an image to another, transitioning from a historic to a contemporary scene. To me, that’s one of the most arresting images on the Internet. The transition between old and new and back again always lends itself to the discovery of new observations – and questions.

When those images are of cities, evolving over time, the tool often allows me to view today’s built environment through a different lens. It helps highlight connections and departures from the city of the past and the city of today.

Britain’s The Guardian posted one such slider a few weeks ago, showing how the London skyline has changed over 400 years. What immediately struck me, aside from the decided lack of steeples on the current cityscape, was the activity centered on and around London Bridge.

In 1616 the bridge, like the Ponte Vecchio in Florence, Italy, was crowded with building and shops. It was far from just a road or a passage. It was a place of activity and commerce and mobility. The bridge in 2016 is just a road – a space for movement.

Where have all our multi-use environments gone?

Last year, when the Tilikum Crossing pedestrian bridge opened in Portland, Stephen Burke at Project for Public Spaces challenged observers and policymakers to consider what more our bridges could offer. Highlighting historic and contemporary bridges that behaved as more than mere passageways, Burke argued that bridge space, especially in urban centers, could be put to more productive use. Activating bridge decks or caps could create the type of engaged space seen in London in 1616.

The new ssss in Portland is the country's largest car-free bridge. Image via flickr/Atomic Taco. The new Tilikum Crossing in Portland is the country's largest car-free bridge. Image via flickr/Atomic Taco.


In recent years, the idea of building additional uses onto existing or new infrastructure has grown increasingly popular, with bridge decks or caps garnering much of the attention. Several parks have been built over expressways in Dallas and Boston — with possible projects forthcoming in Houston and Seattle. Offering updated versions of the London Bridge, Capital Crossing in D.C. is slated to offer a diverse mixed-use campus of 2.2 million square feet atop I-395 in the heart of the nation’s capital. Columbus, Ohio created the Cap at Union Station, a smaller scale set of developments on a bridge over the I-670 in 2004. The new shopping and retail complex helped connect two divided communities.

Klyde Warren Park, opened in Dallas in 2012, sits atop a section of the Woodall Rodgers Freeways. Image via flickr/Dick David. Klyde Warren Park, opened in Dallas in 2012, sits atop a section of the Woodall Rodgers Freeway. Image via flickr/Dick David.


But even if we stop short of turning the top of our bridges into real estate there are countless ways to bring more activity to existing infrastructures. New York’s High Line  jumps out as the most well recognized example, using paths and landscaping to create a place of leisure and interaction.

Simply adding movable commerce such as food carts to the middle of our emerging destination pedestrian bridges could change their character completely. Couldn’t Louisville’s marvelously retrofitted Big Four Bridge, a span made to support hundreds of loaded freight cars, also support additional activities beyond walkers, joggers, and bikers? Pop-ups, the bread and butter of tactical urbanism, could let cities test out what might work on this infrastructure before investing significant money into making lasting changes.

New York City's High Line is a reuse of an elevated railway. Image via flickr/joevare. New York City's High Line is a reuse of an elevated railway. Image via flickr/joevare.


The metaphorical power of bridges as sites for multi-use places is undeniable. They connect, they tether, they link. They allow movement, exchange and interchange. All these are descriptions of healthy, vibrant urban spaces. And they are easy to imagine upon the urban landscape.

But what other urban spaces might we consider adding layers to?

One way to think about the question is to focus on "thick infrastructure." That’s what Susan Rogers and students from the University of Houston’s Community Design Resource Center termed this idea. A few years ago, they created a whole project devoted to the idea that Houston could remake a variety of public spaces into more useful, "thicker" places, with extra layers of use. For example, you could add a farmer’s market to that transit center, or turn that park-and-ride lot into a festival space at night, taking advantage, again, of a temporary use.

So far, Houston has not embraced this idea to any significant extent, but there’s an opportunity for thick infrastructure to make a huge debut in the coming years. With Bayou Greenways 2020, the initiative to create long, continuous parks along the city's waterways, and the Houston Bike Plan each proposing the use of utility easements and public right-of-ways along the city’s bayous for pathways, the opportunity is there for the taking. Rogers and her students made numerous suggestions for these pathways in their initial study. Others should be brainstormed. The more ideas, the better.

These underutilized spaces present not only a chance to reconnect neighborhoods, provide non-road mobility, provide access to nature, and encourage physical activity. They can also be sites of economic redevelopment and may contribute to investment in parts of our urban areas that have been neglected for too long.

When we make an online slide tool for Houston and other cities 20 or 50 years from now, wouldn’t it be great to have future generations wonder at how we decided to turn empty power line easements and underutilized concrete channels into vibrant chains of city life? That’s a shift that would cause me to see the city in a whole new light.