The September book of the month is Killed by a Traffic Engineer: Shattering the Delusion that Science Underlies Our Transportation System by Wes Marshall (Island Press, 2024).
Dr. Marshall is a professor of civil engineering at the University of Colorado at Denver, where he holds a joint appointment in the department of urban planning. He wrote Killed by a Traffic Engineer drawing on his 20+ years of experience as a working engineer, researcher, and professor. You can guess from the title alone that this book is causing a stir in the ITE (Institute of Transportation Engineers) [1].
But let me put it to you straight: safety first is a lie. Safety has never been the top priority. (p21)
That stir is for good reason. Marshall pulls back the glittering green curtain to reveal that the wizards of traffic engineering are not wizards at all, but just men (and they are still mostly men) who rely on bad science and sketchy data to design the streets and roads we all use. Not only that, he managed to write a 400-page book about traffic engineering that is highly entertaining, easy to read, and often funny - no small feat for subject matter that is both dry (lane width, turning radii, level of service) and dire (traffic violence). This is accomplished with short chapters, numerous pop culture references, plain language explanations [2], and masterful use of footnotes [3].
Marshall doesn’t pull any punches:
What traffic engineers are guilty of is creating a transportation system whose designs remain largely based on plausible, but unproven, conjecture…there is less of a link between design and actual safety outcomes than you would think possible…It wouldn’t be hard to argue that this sounds more like a religious cult than a science-based discipline. (p32-33)
A LOT of information is packed into this book [4]. Marshall covers what traffic engineers are doing wrong, how they’re trained, how they approach safety (or not), what data they look at and why, how the various manuals came about and how they are used/misused, how blame gets thrown around and why. Here’s a good example of how a bad, but common, design feature sends mixed messages and turns into victim-blaming if there’s a crash:
…a lot of highway off-ramps have pedestrian crosswalks placed right where the driver needs to merge onto the arterial street. In most places, the chance of seeing a pedestrian in such a crosswalk hovers right around the point of almost never. Traffic engineers also ask drivers to look over their left shoulder toward the traffic they need to merge with instead of toward the crosswalk in front of them. Given the low chance of a pedestrian being present, it isn’t usually a problem. If there is a pedestrian and the driver runs them over, we use hindsight to tell the driver they made a bad decision. They should've seen the pedestrian and stopped to let them cross. Yet this bad decision is one that most drivers in the same situation make every day. And in something like 99.99 percent of cases, that same bad decision doesn’t lead to a bad outcome, nor would it be considered a bad decision to the person making it. (p137)
Marshall breaks down a number of concepts that engineers use all the time and makes them understandable to non-engineers like myself: the 85th percentile rule, the 30th peak hour, stopping sight distance, level of service (LOS) and so on. Importantly, he includes a number of solid suggestions for how this work could be done better, and explains why historically and tragically, not much has changed.
Unsurprisingly, most of this comes down to money [5]. The federal government pays for highways and arterials and distributes more money to states with more miles driven. Cities strapped for cash would be foolish to turn down federal money, so they take it and build dangerous high-capacity roads. The size of insurance claims are based on property damage so that a dent on the door of a luxury car is deemed more costly than a bicyclist’s broken limbs. Fear of lawsuits prevents traffic engineers from designing differently than they always have. There is very little money or creative inertia to do much else.
When we give more money to more miles of arterials, we incentivize classifying more streets as arterials. Look at downtown Denver, where every single street is classified as an arterial. (p208)
But the roots of this are deeply sinister; back when engineers were designing the federal highway system in the 1960s, racist assumptions about “blighted” neighborhoods and cheap land was a primary motivating factor in the routes they chose. Small wonder that the communities situated near those highways are now living with outsized consequences like poor air quality and high numbers of pedestrians struck and killed or badly injured.
Traffic and transportation engineers focus on the wrong things. They continue with business as usual because federal dollars pay for building and expanding highways and arterials. Local laws reinforce “level of service” (aka lots of cars) and have no meaningful requirements for safety. The assumption that engineers have the best and most useful expertise in road design perpetuates the vicious cycle of traffic violence that plagues this country.
The tragic disconnect is that traffic engineers believe they’ve been trained in road safety because they believe the manuals are steeped in a century of road safety knowledge. They aren’t. The reality is that much of what we learn as traffic engineers has nothing to do with actual road safety outcomes whatsoever. That’s why traffic engineers don’t take too kindly to suggestions about road safety. That’s why traffic engineers believe in things that diverge from common sense when it comes to road safety. (p74)
We have come to rely far too much on education and enforcement to address the safety crisis, while working under the assumption that the engineering component is trucking along just fine.[6] We expect humans to behave perfectly in a system that is designed to protect cars instead of people. The hypervigilance required for drivers to pay attention to everything, everywhere, all at once on a road with a 35mph speed limit but designed for actual speed of 55mph or more is exhausting and unsustainable. It’s an impossible standard.
The consequences are getting too big to ignore, but when challenged, engineers tend to get defensive [7]. Here is a list of phrases in “Engineer Speak” often used to deflect criticism:
Safety is a shared responsibility. We need to take a balanced approach. Efficiency. Improvement. Not my job. We need to study the problem further. The standards say…Public participation [8]. (p23-27)
Now before we all pile onto traffic engineers, let’s take a beat and remember that they’re just doing what they’re trained to do. Just about everything in the larger system reinforces that behavior [9]. Very little if anything in their training prepares them to build roads that are actually safe for pedestrians or bicyclists. Very little if anything in our funding mechanisms at the federal, state, and local levels support building safe streets. Big, wide roads with high traffic capacity are incentivized. Not only that, the public has bought into all of this because we have come to expect wide lanes, high speeds, lots of parking, and we treat the space carved out for crosswalks and transit as a nuisance [10]. Like the fish who don't know that water is wet, we are all complicit here, whether we realize it or not.
How do we expect to produce exceptional transportation engineers – or even competent ones – if we aren’t teaching them about transportation engineering, let alone road safety? Why should we be surprised that traffic engineers hide behind our guidebooks and the status quo when we haven’t given them the basic wherewithal to understand their own silo? (p308)
But it doesn’t have to be this way! What if we put safety first, instead of capacity? What if we stopped with the victim blaming already and started building streets for humans instead of traffic projections 20 years from now? What if, for street design, we used the lens of consumer protection instead of level of service? What if we used Marshall’s own formula for creating safer places?
(Kids) + (Active Transportation) + (Transit) - (Parking) = Safer Places (p354)
It turns out a lot of people know better, including Dr. Wes Marshall. His empathy and humanity shine through, especially in the latter chapters of the book when he describes what it’s like to bike through Denver streets and wrestle with the emotional weight of teaching about traffic deaths. Wes Marshall has spent his research and teaching career training young professionals to go forth and design better streets, collect better data, and make the world just a little bit safer for all of us.
Do you want to learn from him, too? Sign up for the webinar on December 4 from 12-1! Register here.
An engineer I know, who shall remain anonymous, attended the ITE conference in July and reported that a council meeting was held for attendees to vent their frustration about the author - wait for it - while he was giving a talk in another room at the same time.
Very approachable, very demure.
There are many references to classic episodes of The Simpsons, and I’m here for all of them.
That’s an understatement.
Doesn’t pretty much everything come down to money?
See what I did there?
White men aren’t used to being challenged. It’s a common affliction.
You could make this a drinking game, but I don’t recommend it.
Kind of like the patriarchy.
"Hell hath no fury like a community that might lose parking." - Veronica O. Davis, Inclusive Transportation
Susan Gaeddert is Community Programs Director at 1000 Friends of Wisconsin, where she runs Active Wisconsin, facilitates the Community Transportation Academy, and coordinates the Wisconsin Climate Table. Have you read any good books lately? Send your recommendation to: susan@1kfriends.org
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