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Kindle Notes & Highlights
by
Wes Marshall
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June 11, 2024 - February 14, 2025
Without people walking and bicycling, we won’t get any pedestrian or bicyclist crashes.
given our safety record, it’s easy to wonder—as James Taylor did in his 1981 Traffic Quarterly paper—“How can one justify spending any money on relieving congestion or reducing delay when these same funds could be used to save lives and reduce serious injuries?”
AASHO inform us in their 1957 manual on urban arterials, “Congestion breeds accidents.”
continuing to fight traffic congestion—even in the misguided name of safety—remains a fool’s errand.
AAA explains in their 1958 pedestrian planning guidebook, zebra crosswalks help make pedestrians more “satisfactory.”
retro-reflectivity doesn’t seem to matter when it comes to crash outcomes.
supposedly better markings were significantly associated with worse crash outcomes.
Instead of trying to understand and fix a system that encourages human error, those behaviors become the problems we try to fix.
In other words, the transportation system that traffic engineers design and build can’t possibly cause crashes. It just sits there, quietly waiting for people to use it. If those people follow the rules that we give them, we’d be 100 percent safe.
we know we’ve designed a system where it’s close to impossible for road users to be completely alert and attentive at all times.
nearly every crash causation study uses the same definition of human error as automotive engineer John Treat did in the 1970s.
between 4 and 7 percent of drivers never look toward the pedestrian before committing to the turn.
the driver is only peripherally concerned about the most vulnerable road user, the pedestrian. We force the driver’s attention elsewhere and hope for the best.
Latent errors refer to the transportation system itself. They are the long, straight, and boring highways. They are
Traffic engineers then treat active errors as random errors, never looking to the latent conditions that lead to their predictability—and to our underlying road safety issues.
It’s our refusal to deal with the latent issues proactively that keeps us spinning our wheels, never making any headway on real road safety improvements.
why not remove the humans altogether? After all, aren’t humans the weak link in the chain? If better education and more enforcement don’t work like we hope, won’t technology save the day?
Car manufacturers will follow Tesla’s lead and make you agree to taking over the manual controls whenever there is a problem, which keeps the blame on the road users.
We thus overestimate our ability to predict what would have prevented the crash. We reverse engineer the outcome.
The reality is that, in transportation, most bad decisions lead to perfectly fine outcomes.a In such cases, we rarely know we made a bad decision. Pointing out a bad decision, in hindsight only after a bad outcome happens, doesn’t much help the cause.
The responsibility to do better needs to be placed in the lap of traffic engineers. Instead, the hindsight and counterfactuals help us feel like we have a simple human error explanation.
“America is all about speed, hot nasty bad-ass speed.—Eleanor Roosevelt, 1936.”
We measure the 85th percentile speed and set a higher speed limit. Drivers perceive this new limit as their low-end target speed, and they drive a little faster. We measure the 85th percentile speed again. It’s higher, so we set an even higher speed limit. So on and so forth.
We slowly but surely manufactured a hypothesis where “pace” was the only thing that mattered. Raw speed? Raw chicken? Who cares?
(AASHTO) defines design speed simply as “a selected speed used to determine the various geometric design features of the roadway.”
for another decade, AASHTO continued to tell us that “every effort should be made to use as high a design speed as practical to attain a desired degree of safety.”
we end up designing our roads to placate and protect those that think they are in the next Fast and Furious movie. This isn’t the road to safety.
How about instead of treating the design speed as something close to the uppermost limit, we set it as a target speed?
average American adult male (weighing close to 200 pounds) would have to bicycle at 120 mph to create the same kinetic energy as a typical sedan at 30 mph.
“Mathematically, higher speed leads to reduced travel time. However, the effects of speed in reducing travel time are generally overestimated by road users and, at least in urban areas, the time savings are often small or negligible because of intersections and delays at traffic lights.”
The National Safety Council estimated that we saved 40,000 lives between 1973 and 1979, half of which the council attributed to a lower speed limit.
lower speeds helped save between 2,000 and 4,000 lives each year.
2009 study “estimated that higher speed limits across the United States led to 12,545 excess deaths” and “36,583 injuries in fatal crashes” in the ten years after Congress repealed the national maximum speed limit
Another problem is that we like to leave speed up to “personal responsibility.” But sadly, more than 35 percent of those who die in speeding-related road crashes are not the people who were speeding.14 I may be crazy, but I see a big difference between allowing your lack of personal responsibility to kill yourself versus your lack of personal responsibility killing innocent people.
The design hourly volume typically equates to the 30th highest hourly volume.
American Association of State Highway Officials (AASHO) says in its 1957 manual specific to urban arterials, “Design capacity must be sufficient for the design-hour volume.”
A 1957 Traffic Quarterly paper suggests we should assume a 5 percent compounding traffic increase.
design vehicle.a The main idea is to design streets for the biggest and least maneuverable vehicle that may use it.
the combination of our main three design criteria has systematically led to the creation of the deadliest streets in most every city.
At best, the research is inconclusive. At worst, wider traffic lanes lead to higher speeds and less safety.
The solution? “We’ll need a bigger road!” And everyone falls onto their backs and laughs uncontrollably, which, if you’ve seen Peppa Pig, makes a lot more sense.
traffic engineering outcomes are often counterintuitive and that traffic engineers have a history of overlooking the disconnect between what we think leads to better safety and what actually does.
the clear zone includes shoulders, which makes some sense, as well as bike lanes, which doesn’t make any sense.
transportation planners to “unconsciously fill in the bits missing from the current evidence in accord with their theories.”
“One-half of urban fatal accidents involve pedestrians.” Well, that sounds bad, but shouldn’t we design to help pedestrians instead of trying to eliminate them? “Pedestrian movements and congestion, augmented by intersectional and roadside interference, are the chief causes of urban accidents.”
“Chief MacDonald insists that we must dream of gashing our way rather ruthlessly through built-up sections of overcrowded cities, in order to create traffic ways capable of carrying the traffic with safety, facility, reasonable speed.”
The real problem? All the stubborn people who won’t leave their homes and move to that farm upstate. Hoffman starts by saying we need “a new land policy.”
Evacuating a Large City in Case of Atomic Attack,” the basic premise is that the Russians will kill us if we don’t have freeways in cities.
Mythbusters—but without presenting actual evidence—Russell Singer sets out to bust some myths about problematic urban freeways.
A 1953 Traffic Quarterly paper describes new urban highways as a good way to remove or cordon off the slums: “In each case, the highway locator has an opportunity to assist the community in the redevelopment of depressed areas and to open up for good development other areas not otherwise progressing.
