In 2015, an urban planner in Arkansas created this meme, Which street is safer? They're both residential streets with a 20 mile per hour speed limit. But while this street was designed to be more forgiving to drivers, this is actually the safer street. So, why have we been building so many streets like this one over the past 50 years? In 2017, traffic deaths hit a 25-year-high of 40,000 fatalities. Six thousand of those killed were pedestrians. Cities across the country are trying to reduce traffic fatalities with safety campaigns. One of the keys to the whole problem might be a flawed mid century design philosophy. There was a big transportation safety movement in the 1960s. This is when we saw the development of airbags and crash tests. In 1965, Ralph Nader published a book about the designed-in dangers of cars and roads. He accused car companies of resisting safety improvements in order to cut costs. The book was a best seller. It led to Senate hearings, which then led to the creation of the Department of Transportation, which eventually led to the creation of the National Highway Safety Administration. There were two key testimonies during congressional safety hearings in 1966 that paved the way for a flawed approach to street design. One was Ralph Nader. Where our safety laws had previously been about enforcing safe driving behaviors like following the speed limit, Nader's testimony led to a shift in thinking. He said, "Even if people have accidents, even if they make mistakes, even if they are looking out the window or they are drunk, we should have a second line of defense for these people. The sequence of events that leads to an accident injury can be broken by engineering measures, even before there is a complete understanding of the causal chain." The other key testimony came from a senior engineer at General Motors. Ken Stonex helped GM Design a so-called crash proof highway test site called " The Proving Ground". What happens when a front tire blows at 90 miles an hour? Let's find out. Perfect control, basic built-in stability. The proving ground had wide clearances, 100 feet on either side of the roadway, as a safety measure for drivers. Crash data from the proving ground showed that most cars that ran off the road came to a stop within 30 feet. The committee at the hearing seized on this data. One of the main sources of traffic fatalities at the time was single vehicles running off the road and colliding with a fixed object like a tree or light post. Stonex testified that we should operate 90 percent or more of our surface streets just as we do our freeways, and that we should convert streets to proving ground road and roadside conditions. By 1967, the 30-foot clear zone was adopted into the official standard for road design. The Nader and stonex testimonies reflect a bigger idea called " Forgiving Design". The thinking goes,"No driver is infallible, mistakes will be made. So, let's design our roads and streets with that in mind to be as forgiving as possible when a driver does make inevitable errors, they've got plenty of room to regain control." The critical flaw in this thinking, this design doesn't account for how drivers would adjust their behavior in a forgiving environment. A forgiving environment has wide clear shoulders, wide straight travel ways, high visibility. But when you drive on a street like this, something happens. Your brain perceives this as a safe environment. So, even if the posted speed limit is 20 miles an hour, that subconscious feeling of safety means your speed tends to creep up and up. If you remember drivers Ed, you remember, speed kills. He always draw too fast and that's what caused the accident. When you're hit by a car going 20 miles an hour, nine out of 10 times you'll survive. But as speed increases, the numbers get pretty grim. So, urbanists and safety advocates are trying to get us to think about how we can slow drivers down when we're not on highways. Streets like this one with its tree canopy and narrow lanes were actually outlawed when The Forgiving Design Movement took hold. This street looks and feels more hazardous to a driver. You don't have great visibility, you have to weave around parked cars in a narrow lane, sensing the inherent risk in the environment, you tend to take things a little slower, no matter what the posted speed limit says. Does this mean that Stonex's proving ground data was totally wrong? Not at all. But he and other transportation engineers collapsed an important distinction. There's a difference between roads and streets. Roads are simply about connecting to places. They're designed to facilitate speedy, efficient movement. Streets are about building place and economic value. So, over the last decade, urbanists have begun to call into question the old forgiving design philosophy. Forgiving design is forgiving to drivers at high speeds on highways and arterial roads, but it's not the safest design for urban streets where you've also got to think about pedestrians and cyclists. It's a case of the design not matching up with the use. But now that Urbanists have pointed out the problem, we're starting to see a return to design elements that subconsciously encourage drivers to take it slow. Thanks so much for watching. Hit the comments to let us know if you had any examples of excellent or a terrible road design where you live, and hit the bell icon to be notified next time we post a video. See you next time.
Great post. The never ending struggle between designers and engineers.
TELL THE NORMIES
Fire Departments seem to be the most resistant to change. Citing response times as their reason for wide roads. Even though the majority of their calls aren’t fire related, and smaller, equally as capable trucks are available.
This is pretty well known in planning circles at this point, but it's good to see the idea gain traction.