The Q’eswachaka Bridge spans a gap 120 feet above the Apurimac River in the Andean mountains. The bridge has been a critical local connector for seven centuries despite being constructed only of grass.
The local communities gather annually for a three-day festival at the bridge, where they cut loose the existing bridge and suspend a new one woven from grass. This begs the question: Is it the same bridge if they remake it each year?
This example comes from the book “How Infrastructure Works” by Deb Chachra, a professor at the Olin College of Engineering. Among her insights is that infrastructure is defined not by the physical materials that construct it but by the connections it makes.
Infrastructure has a powerful effect on the world and our everyday work. Consider the women’s suffrage movement. The suffrage movements of the United States, the United Kingdom and Canada grew in tandem with the introduction of water, sewage, gas and electrical systems. Absent basic infrastructure, women spent far more time providing necessities for their families. Basic infrastructure freed up time to organize and press for more rights.
Today, the opportunity exists to continue enhancing infrastructure and the connections it makes through greater pedestrian safety and accessibility.
Last September, the U.S. Access Board issued its final Public Right-of-Way Accessibility Guidelines (PROWAG). The rules, which resulted from a 24-year process dating to 1999, “address access to sidewalks and streets, crosswalks, curb ramps, pedestrian signals, on-street parking, and other components of public rights-of-way.”
While the news largely flew under the radar for most Americans, the new guidelines will profoundly affect how we enhance safety and accessibility in our communities. PROWAG provides a much-needed, clear standard for states and cities to follow as they look to upgrade their pedestrian infrastructure. This is important not only for people with disabilities but also for joggers, bikers, moms pushing strollers and many others.
We’re all better off when we have safe sidewalks free of trip hazards and that provide clear crossing signals and enough time to cross, and other pedestrian safety features.
Infrastructure becomes more valuable to all as accessibility increases. In computer science, Metcalfe’s Law states that the value of a network increases proportionately to the number of connections to each node. In her book, Chachra applies this concept to infrastructure, citing that early water systems could be a tough sell to wealthy residents who could afford clean drinking water. But because water-borne diseases are communicable, the value of potable water is realized only when everyone has access.
As it relates to the new PROWAG guidelines, when a sidewalk or facility is accessible to all, its value increases. A sidewalk connecting only two houses is of limited value even to the two households connected to it. Just one connection. But if it’s extended to reach 10 houses, then you have 45 total connections that can be made. (This is represented mathematically through the number of nodes, n: connections = (n(n-1))/2. Each additional node to the network adds n-1 new connections. Get all the way to 99 houses and a grocery store, and you’d have: (100(100-1))/2 = 4,950 connections!)
People with disabilities have much to contribute to society. As we improve accessibility or remove barriers to access, their participation in the economy will grow. Nearly one out of five Americans and half of people over 65 have a disability, according to the Census Bureau. Since companies began allowing more remote work in 2020, there has been a 28 percent increase in the number of people with disabilities participating in the labor force. That’s 1.8 million workers added to our economy, with much more power yet unleashed.
There are, of course, other cases to be made about equity and inclusion pertaining to public infrastructure, but the economic argument is too often ignored.
And what is more accessible for people with disabilities is also safer for all pedestrians. Our public policy must take the view that infrastructure is not about the physical steel and concrete that make it up but instead about the connections it creates. And through the power of Metcalfe’s Law, we can unleash economic growth as we add and enhance those connections.
