Professor Wes Marshall is blowing the lid off site visitors engineering in his new ebook, by questioning its very foundations. Right here he shares a few of what was uncovered in his analysis into the historical past of the self-discipline; his hopes for the long run; and the opportunity of constructing roads which are safer by design
If we have to consistently remind folks within the transportation system to be protected, is it actually a protected transportation system?” This provocative query is on the coronary heart of Wes Marshall’s ebook, Killed by a Site visitors Engineer, which challenges the foundations of contemporary highway design and site visitors administration.
Human error is usually cited because the main reason for crashes; when a crash happens it’s normally stated that somebody didn’t observe the foundations of the highway… they weren’t being ‘protected’. But when the design of the highway is such that the foundations are extremely troublesome to observe, is the design actually protected within the first place?
Regardless of its eye-catching title, the ebook isn’t about shifting blame however rethinking assumptions which have guided the sphere for a century. Marshall speaks to TTi from his college workplace, the window behind him displaying a busy, well-kept freeway with vehicles blinking again the morning solar as they velocity previous. This freeway appears to be working successfully and assembly the wants of residents, following design requirements constructed up over many years, so absolutely it’s properly designed? Not essentially. In his ebook Marshall, himself a site visitors engineer, argues that going again to the drafting board and rethinking present steering might actually save lives.
“What made me offended was that the stuff I used to be taught, I simply assumed was steeped in 100 years of security analysis; that this was all making our roads safer,” he explains. “Once I began digging down a few of these rabbit holes, it simply wasn’t true. There wasn’t security embedded in that type of stuff.”
“I’m not blaming site visitors engineers,” he provides. “I’m saying we have been doing what we have been taught, however that isn’t what we expect it’s. It’s not as scientific as we have been ever led to imagine.”
The place did all of it start?
The AASHTO Inexperienced E-book, the USA’s information to freeway and road design, started as an effort to standardize practices throughout states. “They have been attempting to ensure we didn’t have inexperienced cease indicators in a single state and purple in one other,” Marshall says.
This laudable mission began in pamphlet kind and grew into the excellent handbook of immediately. However when Marshall appeared up the unique research behind many design requirements, he was shocked by how skinny among the proof was. “Once you have a look at among the issues we do, it’s important to dig down fairly deep to search out the preliminary research,” he says. “You’re like, ‘Wait a second, that’s the research? That’s why we do it that manner?’”
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Typically flimsy analysis has been compounded over time by the truth that higher options can really feel counterintuitive. For instance, whereas engineering instinct suggests wider lanes are safer as a result of they supply more room, the information doesn’t help this.
“It might be the case if we people behaved the very same manner on each of these streets,” says Marshall. “Once you put a wider highway in entrance of people, we behave otherwise. We begin driving quicker.”
New information reveals that wider lanes usually result in extra harmful circumstances.
Surprisingly, the unique research from the Twenties and 30s solely examined roads as much as 24ft broad curb-to-curb – narrower than many trendy roads. “Possibly 24ft is safer than 18ft,” says Marshall. “It doesn’t imply that 60ft, 80ft or 120ft is safer than 30ft.”
Rethinking freeway design
In his ebook, Marshall suggests plenty of methods to treatment the issue of badly engineered roads, together with a basic rethink of the present method to road design. “The way in which I used to be taught to design a road is you begin from the middle line,” he says. “You determine how a lot area we have to give to vehicles, and also you begin working your manner out. On the finish of the day, no matter’s left over, we give to pedestrians; and typically it’s nothing. If we put our cash the place our mouth is, we’d design from the skin in. How a lot area do the pedestrians want? How a lot area do we want for bicyclists and transit? No matter’s left over might go to vehicles.”
This method displays the upside-down pyramid of transportation priorities that many cities declare to observe – pedestrians first, then cyclists, transit, freight, and at last vehicles – however hardly ever implement in apply.
One other downside Marshall identifies is the give attention to ‘stage of service’ – a measure of how effectively site visitors flows by means of a system, which frequently extends to catering for predicted future service necessities. “I used to be taught that if we do that, issues can be safer,” he says.
However when he investigated the origins of stage of service requirements, Marshall discovered a haphazard historical past, with a handful of individuals attempting to review congestion at a time when it actually wasn’t an issue, and utilizing straw polls to attempt to set up what could be required.
“We have been doing what we have been taught, however that isn’t what we expect it’s”
Whereas early specs talked about including security to those requirements, subsequent iterations eliminated these necessities. “We by no means added security to it,” says Marshall. “If we truly have a look at the best way we’re centered on these site visitors influence assessments… that form of stuff is making our roads much less protected.”
Marshall is eager for the long run however believes site visitors engineering must embrace a extra scientific method. “Medical doctors have been round for five,000 years, however for the primary 1,000, you might argue that they have been killing greater than they saved,” he says. “Site visitors engineering is barely 100 years outdated. We’re nonetheless within the stage the place we’re killing extra folks than we save. The issue is we don’t understand it. We expect we’re this fully-fledged science.”
Drawing inspiration from Donald Shoup’s work on parking rules, Marshall advocates for extra empirical rigor. “Medical doctors do trials, take a look at completely different medication, work out what occurs, and so they get higher and higher, slowly however absolutely. We have to try this to get higher.
“Thirty years from now, we might look right now because the Darkish Ages of transportation engineering. Once I have a look at what we’re doing and why, it seems like that’s true. We are able to do higher. That’s the underside line.”
ABOUT WES MARSHALL
Wes Marshall, PhD, PE, is a professor of civil engineering on the College of Colorado Denver, the place he holds a joint appointment in city planning. He performs a pivotal position as director of the CU Denver Human-Centered Transportation program and the Transportation Analysis Heart at CU Denver. Marshall focuses on transportation instructing and analysis devoted to creating safer and extra sustainable transportation methods. He’s a recipient of the Eisenhower Transportation Fellowship, Australia’s Endeavour Fellowship, and the Transportation Analysis Board’s Wootan Award for the excellent paper in coverage and group.
Podcast Additional
Take heed to the complete model of this interview in Episode 48 of the Transportation Podcast from Site visitors Know-how Worldwide
This interview was first printed in the Might 2025 version of TTi journal
