Engineers Should Not Design Streets

[M II A II R II K]

Engineers Should Not Design Streets


May 6, 2021

By Charles Marohn

Read More: https://www.strongtowns.org/journal/...design-streets

.....

Roads and streets are two separate things. The function of a road is to connect productive places. You can think of a road as a refinement of the railroad, a road on rails where people board in one place, depart in another, and there is a high-speed connection between the two. In contrast, the function of a street is to serve as a platform for building wealth. On a street, we're attempting to grow the complex ecosystem that produces community wealth. In these environments, people (outside of their automobile) are the indicator species of success. So, in short, with a street we're trying to create environments where humans, and human interaction, flourish.

- Engineers are well-suited to constructing roads. Road environments are quite simple and, thus, lend themselves well to things like design manuals and uniform guidelines. There are only so many variables and the relationship they have to each other is fairly straightforward. In the United States, we have tested, refined and codified an engineering approach to roads that is pretty amazing and, in terms of engineering, the envy of the world. — There are two primary variables for designing a road: design speed and projected traffic volume. From those two numbers, we can derive the number of lanes, lane width, shoulder width, the width of clear zones and the allowable horizontal and vertical curvature. From those factors, we can specify all the pavement markings and signage that are necessary. We can then monitor things like the Level of Service, the 85th percentile speed, and traffic counts to optimize how the road functions over time. Engineers are really good at this.

- Engineers are not good at building streets nor, I would argue, can the typical engineer readily become good at it. Streets that produce wealth for a community are complex environments. They do not lend themselves well to rote standards or even design guidelines. There are numerous variables at play that interact with each other, forming feedback loops and changing in ways that are impossible to predict. — Consider just one variable: the future of the adjacent land. The operative component of building wealth on a street is building. Who owns the property? What are they going to do with it? What is their capacity? Will they stick with it? Will they find the love of their life and move across the country? Each property has a near infinite set of complexities to it that change and respond to change, each of which is far more important to the wealth capacity of the street than, for example, lane width.

- So if this isn't the job of an engineer (and it's not), then who should design streets? The answer is as simple as it is radical: everyone. Building a productive street is a collective endeavor that involves the people who live on it, those who own property on it, and those who traverse it, as well as the myriad professionals who have expertise they can lend to the discussion. — Put your least technical person on staff in charge of your next street. Empower them to meet with people, observe how people use the street and then experiment, in a low cost way, with different alternatives. Keep experimenting until you start to see your indicator species show up outside of their cars, of course. Now you have a design you can hand over to your engineer to specify the technical stuff (pavement thickness, paint specs, etc.) and get the project built. — When you are trying to make your city wealthier and more prosperous—make your engineer one small voice in a larger chorus of people whose words and, especially, whose actions dictate what your design should be.

.....