Traffic engineering as a field has a somewhat false image that it has been around forever and all the manuals and guidance are steeped in centuries of research and practice, when in fact, the field has barely reached one hundred years and much of its foundation is questionable research. Killed by a Traffic Engineer: Shattering the Delusion that Science Underlies Our Transportation System by Wes Marshall points this out and over the course of eighty-eight short chapters shatters the illusion that traffic engineering is as methodical as it seems. The problem lies in the fact that early on in the profession, traffic engineers had little to go on and developed manuals based on thin evidence. The next generation of traffic engineers came and trusted their predecessors knew what they were doing and so on. As Marshall states in the book, “This undeserved faith has stifled the science.”
The comparison is made to the medical field which has been around significantly longer than traffic engineering, but similarly in its early years more people were dying than were being saved because it was an early science and mistakes were made. Readers will quickly learn that Marshall is not implying that traffic engineers are maliciously killing road users, but that the underlying foundations of traffic engineering have led it to be the most deadly form of transportation we have. In 2021, an average of 118 people died on our roadways each day. Our roadways have not been designed to increase safety. Instead, designs are focused on moving cars fast and reducing congestion.
Traffic engineering is hitting an inflection point where it can continue as it has based on flimsy data and resistance to change or make great strides to return to a more scientific field that overhauls its manuals, most of which are guidebooks and not strict rules, to reflect new knowledge and a focus on safety of all road users.
There are many great books sounding the alarm on our transportation system, many of which have been covered on the Booked on Planning Podcast, including Angie Schmitt’s Right of Way and Bicycle City by Dan Paitkowski just to name a few. What’s interesting is to avoid being biased by other works, Marshall avoided reading anything related to the transportation field, whether a recently published book or article, while writing Killed by a Traffic Engineer. The book relies on journals and articles published in the infancy of the field, demonstrating the lack of evidence behind many requirements as well as the fact that these same rules have never evolved.
It can be hard to understand as an outsider to the transportation engineering field why these manuals carry such weight and have yet to change, despite all the recent evidence that the rules lack any of their own. It is frustrating watching from an adjacent field that is so greatly impacted, usually negatively, by the Manual on Uniform Traffic Control Devices (MUTCD) knowing there is little science behind much of its requirements. If a community has identified a need for a pedestrian signal crossing it should not need to wait for some arbitrary number of dare devils to make the unsafe crossing first before it is deemed warranted.
Change is hard, no matter the subject or field. Traffic engineering is making slow strides in the right direction, however they have yet to change the fundamentals of the system. Without those necessary changes, the profession has stagnated. An example of this is in the recently released 11th edition of the MUTCD and its guidance on the 85th percentile. This rule sets speed limits based on the speed 85 percent of drivers are traveling slower than, effectively making the speed limit what the fastest 15 percent of drivers are willing to go. This creates a negative feedback loop where speed limits continue to go up as drivers adjust to the new limit. The new MUTCD had the opportunity to do away with this regulation which is clearly a faulty measure, but instead maintained it with guidance that it not be a primary factor but considered with other contextual factors such as land use, pedestrian activity, crashes, and others.
“Fundamentally changing our transportation system means fundamentally changing the traffic engineering discipline that created it.” In this call to action that comes in chapter 87 of 88, Marshall voices the need to approach education and enforcement on our roadways differently, stop waiting around for technology to save the day (because it won't and has more potential to harm than help), and reframe how we invest our money for roadway improvements.
The final chapter is Keep Asking Why. We should keep asking why we do what we do, a license to be that annoying kid again that keeps pushing why until a real answer is obtained. That’s the way it has always been done and because the manual says so are no longer good enough answers to a design decision. We should push to get painted crosswalks that enliven a downtown district or setting lower speed limits to reduce fatalities rather than accept the questionable science backing the manuals as the best answer.
Killed by a Traffic Engineer: Shattering the Delusion that Science Underlies Our Transportation System by Wes Marshall, with its 88 short chapters is actually a quick, informative read filled with pop culture footnotes that provide comedic relief to some of the heavier content covered in the book. Any lay person should be able to pick this up off the shelf and, after finishing it, have a better understanding of the principles of transportation engineering and be armed with arguments against warrants and any other arbitrary request made based on outdated or simply wrong research.
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