Did You Save Anyone Today?
This Strong Towns member-submitted article was originally published in the Institute of Transportation Engineers’ Florida-Puerto Rico Division newsletter. It is shared here with permission. In-line photos were provided by the writer.
Back when I was a traffic operations professional, my then-wife came home from her job as head nurse at a hospital’s ICU and announced with some pride that she had saved a life that day. She went on to describe the person and the situation, along with how she saved his life. When she finished, I told her I had also saved a life that day — I just didn’t know who it was, and neither did they. I was preventing crashes by optimizing signal timing, revising intersections, adding and maintaining signs and pavement markings, and even doing a road diet on a major street before anyone thought of the name. I was saving lives by practicing my profession exactly as it was taught.
Perhaps. But was I also causing harm by taking those same actions? Are transportation planners and engineers routinely making design choices that harm people by optimizing speed and capacity for motor vehicles over all other considerations? Authors Wes Marshall and Charles Marohn say we are.
Marshall’s book, "Killed by a Traffic Engineer," recommends policy changes similar to those in the Strong Towns movement, where Marohn has written extensively about how we build highways and then ask them to function as streets, what he calls “stroads.” (See "Strong Towns: A Bottom-up Revolution to Rebuild American Prosperity" and "Confessions of a Recovering Engineer: Transportation for A Strong Town.")
Marshall notes that many design standards and operational guides applied by traffic engineers were founded on whatever data they had at the time. Here, we are talking about the 1920s to the 1950s. In most cases, there have been no updates. “Good enough for now” turned into “It must be done this way.” Some “standards” were the products of lobbying and propaganda from the auto industry — a way to not only make the environment favorable for cars but also make cars necessary for everyday life. The entire suburban design philosophy used in this country since World War II has been intended to sell cars. It argues that the traditional grid street pattern is out of date. Cul-de-sac streets in isolated subdivisions that are built all at once, each with a single point of access to the major highway network and few, if any, cross connections, are much better. This design pattern was intended to make geographically close locations far apart in terms of street travel distance. Marshall calls it the “tree design approach.” Needing a car to go almost anywhere isn’t a bug; it’s a feature.
The title of Wallace’s book comes from his conclusion that we are collectively putting vehicle capacity at the top of our design parameters while assuming that safety will “just happen” if we follow the established roadway design standards. Marshall clearly demonstrates that there has never been any factual basis for assuming these design standards improve the safety of vehicle occupants, pedestrians, and cyclists, or that they provide a societal benefit.
Marshall subtitles his book “Shattering the Delusion that Science Underlies Our Transportation System,” implying that science does not, in fact, form the basis of our current roadway design standards. On this point, I must disagree. The sciences of marketing and lobbying are very much proven by what he reveals in the book. However, to his point, I had already seen some of these “gaps in the science.”
As a member of an NCHRP panel that developed the original "Highway Safety Manual," I had already discovered that many of our standards are weakly supported. The first eight signal warrants, for example, were devised by traffic engineers sitting in a hotel room back in the 1930s. Marshall’s examples include design-hour volumes (devised in 1941, based on 89 counts in 43 states); 12-foot lane width (a 1938 policy decision by an AASHTO committee); 30-foot clear zone (based on a 1965 review of 507 run-off-the-road crashes); perception-reaction time for yellow signal timing (devised in 1925 for reaction time and 1934 for perception time); and using the 85th percentile speed for determining speed limits and design speeds. Marshall critically analyzes the practice of projecting future capacity requirements as a basis for design.
Marshall saves his strongest criticism for the big evil: functional classification, where we balance mobility and access. The problem is that classification decisions are substantially arbitrary and seek to apply standard sections that lack the adaptations necessary to fully accommodate all situations — in other words, they follow a "one size fits all" approach. As a result, we build six-lane divided highways through the center of towns and then wonder why so many pedestrians and bicyclists are killed, why no one walks anywhere, or why people are going so fast.
The cross-section difference? The urban segment has curbs. Do you think the drivers notice?
Marshall and Marohn don’t just blame marketing and old data for our current unsustainable development patterns. They also fault us, the people who follow the unsupported design and operational guidance that makes Vision Zero a pipe dream.
Marshall traces the core problem to the poor training of professionals in transportation planning and engineering. We are taught what to do but not why — and that information is the key to everything. We should have asked, “Why is this safe design?” If we had, we would have seen the standards we apply are almost completely made of shadows and inferences. Maybe an engineering education is too restrictive. Maybe we could use a broader set of qualifications, as Marshall appears to say in his book, for the very reason that traffic is not a deterministic animal. It’s like the 2011 movie "Moneyball," where statistical analysis overtook baseball knowledge as the key to fielding the best team.
However we got here, Marohn and Marshall argue that it is a bad place and we must change course. As evidence, they point to the persistent inability of our design standards — and the billions spent on road and street construction that conforms to those standards — to actually improve highway safety. As Marshall writes, “Under the old view, the system is safe, and people are the problem.” If only people would do what they are supposed to do! Although we can predict with absolute certainty that people will not perfectly follow the rules all the time, we design roadways on the assumption that they will. We need to stop doing that. Our design standards need to anticipate that people will make mistakes.
Stroad (left) vs. street (right). Which roadway do you want to cross?
The big question then, of course, is how can we change? How can we begin to critically view sources like the AASHTO Green Book or the "Manual on Uniform Traffic Control Devices"? My hope is that engineers love to solve problems, so once a problem is identified, we will begin to work on solutions. Mechanisms like the "Florida Design Manual Context Classification Guide" can serve as a platform for change. The Institute of Transportation Engineers itself must be in a leading role in this regard, with the Florida-Puerto Rico Division at the forefront, as Florida’s dynamic development environment and our extensive knowledge of it puts us in the best position to try new approaches — ideas based on actual research findings.
We need to first understand the problem, the real problem, before embarking on another set of solutions that merely look right. Explore the writings of Marshall, Marohn, Peter Norton ("Fighting Traffic and Autonorama"), and Susan Handy ('Shifting Gears: Toward a New Way of Thinking about Transportation"). And then ask, “Why?”
Strong Towns Member Jack A. Butler is a certified planner, board member for the American Institute of Building Design, and co-owner of a residential design and build firm. Jack is also a former city manager, transportation planning consultant, computer system designer, book author, and professional race car driver. He was named AIBD’s Designer of the Year in 2023.
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