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traffic safety

Design-Oriented Traffic Safety Vs. Passive Safety

U.S. traffic safety has eroded compared to other countries. Focus on passive safety measures is partly to blame. (Graph from NYTimes)

While I was recuperating from my fall this winter, I spent a lot of time reading about international development and public health. “Poor Economics” by Abhijit V. Banerjee and Esther Duflo caught my attention because it makes an empathic case for understanding the cycles of disease and poverty, and explains how small, incremental changes can have huge benefits for vulnerable populations. On a case study of Ugandan school system corruption, for example,  embezzlement by district officials was reduced substantially by publishing school financial information in the papers. Once the information was public and officials were held accountable, corruption was reduced and schools received most of the money owed to them.

The example above implies that sometimes systems and institutions designed to provide public services fail, and when they do, work-arounds are needed. Banerjee and Duflo site the three “I”s as the primary problems facing well-meaning but failing institutions; ideology, ignorance, and inertia. While the authors use these concepts to explain international development studies in third world countries, they can also be used to explain many failing street design policies which have contributed to automobile domination in our public spaces, significant loss of life on our streets, and the entrenched auto-centric culture prevalent in many state and local DOTs.

I’ll explain why this is important. While places like the Netherlands have taken an active, grass roots stand against reducing road injuries and fatalities through safer road design, the U.S. has 32,000 traffic deaths a year (about a 60% higher per capita fatality rate than the Netherlands) and road design isn’t even remotely within our national public discourse. We tacitly accept these roadway injuries and fatalities as acceptable collateral damage for the privilege of owning and operating a personal vehicle in the most convenient way possible; excessively wide streets, insane roadway standards which encourage speeding and auto dominance, and alternative modes as mostly an afterthought.

Still, despite its head start and that cocoon of technology, the nation has steadily slipped behind other countries, becoming comparatively one of the most dangerous places to drive in the industrialized world. -Tanya Mohn, 2007, New York Times

Our auto culture has been dominated by passive safety measures. Bulkier cars, airbags, clear zones, wide streets; basically making our streets idiot-proof for motorists who want to drive as fast as possible. While total traffic deaths have decreased since 2005, and some passive safety devices have helped, pedestrian and cyclist deaths are on the rise. The core idea of passive traffic safety in the U.S. came from William Haddon, a medical doctor who teamed up with Senator Patrick Moynahan and Ralph Nadar in the late 1950s and 1960s to push legislation which protected drivers at all costs without influencing their behavior.

The orthodoxy of that time held that safety was about reducing accidents–educating drivers, training them, making them slow down. To Haddon, this approach made no sense. His goal was to reduce the injuries that accidents caused. In particular, he did not believe in safety measures that depended on changing the behavior of the driver, since he considered the driver unreliable, hard to educate, and prone to error. Haddon believed the best safety measures were passive.  – Malcolm Gladwell, The New Yorker, 2001

Passive safety was pushed at the expense of more holistic, design-oriented solutions which protect vulnerable road users and slow traffic. The problem isn’t mandating seatbelts and air bags; they save lives. The problem is focusing on passive safety and completely ignoring design. Driving behavior must be influenced for safer streets.  I still hear planners and engineers quoting Haddon, not fully understanding where the ideas came from or how the ideology has failed at creating livable streets.

So, getting back to the 3 “I”s, here’s how they apply to institutions which have influenced road design in the U.S. during the past 50 years:

  • Ideology: Traditional U.S. auto culture has pushed passive safety measures as king. Haddon, Moynihan and Nadar are mostly responsible for this 50 year old ideology. It needs to end.  Core ideas which have influenced road design and should now be questioned: “If the driver protected, that’s all that counts.” “If all traffic is going the same speed, no matter how fast, the road is safe.” “Clear, obstruction-less streets are best.” “Roads are designed for cars because almost everyone drives and that’s how Americans want to get around.” These ideas have been pervasive at the local, regional and national level and are outdated at best.
  • Ignorance: Many people who design streets may not actually spend time on them or understand how they work, or if they do, their only perspective is through a windshield. Experience is underrated and actually getting out into the neighborhood to see how streets are used (or would like to be used by communities) fills in a lot of knowledge gaps. On a personal level, streets are one of the few remaining public places in many neighborhoods, and top down, myopic engineering standards are often inadequate at dealing with the nuances of their use by communities.
  • Inertia: Most people in the U.S. as well as state and local DOTs have gotten so used to fast, wide, mono-use streets that anything which may interfere with free flowing traffic at maximum speeds  is deemed sacrilege. It’s just easier to keep the gears turning instead of having to fight with the powers-that-be about why you want to convert a traffic lane into a cycletrack.

While the U.S. threw up its arms and said, “We’re not going to change driving behavior so we might as well protect the driver”, the Netherlands saw road fatalities as unacceptable and that sensible road design was a way to make streets safer for everyone, even if it means de-prioritizing the automobile through a cultural shift.  The Netherlands instituted traffic calming, shared spaces, road diets, and other measures at a national level and saw results. The country refused to accept needless carnage on its streets.

While we can do the same in the U.S., it’s more of a challenge. The auto culture is more entrenched. The country more expansive and diverse. But we can start on the path of sensible road design by washing away the three “I”s mentioned above and fundamentally rethinking our roads using these 5 axioms:

  • Design influences behavior. Build streets more human-scaled, and drivers and pedestrians begin to act as equals. Build streets as highways, and automobiles dominate the space.
  • Speed is the enemy. This goes against almost everything traffic engineers learn in school, but agencies have to stop being afraid to inconvenience motorists. I don’t care if it’s a major arterial road that an important politician drives on everyday. Traffic speeds over 35mph are more likely to kill drivers, pedestrians and cyclists, and every single element of street design needs to communicate to drivers that speed is not acceptable.
  • Material collateral damage is acceptable.  Trees, curbs, narrower streets, unique intersection angles, medians and the like which slow driver speeds at the risk of low-speed collisions with a fixed object are OK.  Vertical elements are good. Remember the first axiom: If drivers sense they no longer dominate the road, they will slow down and be more attentive to their surroundings. I’d rather have a driver hit a tree at 15mph than careen into a sidewalk at 35mph.
  • Human collateral damage is unacceptable. This should go without saying, but given the fact that we design many of our streets like highways, sometimes I think U.S. auto culture values speed and convenience over human life.
  • A street is a place first, a conduit second. As Mikael Colville-Andersen mentioned, we’ve gotten into the habit of engineering something that is, by nature, very organic and personal. Think of the street where you grew up. Do you describe it using level-of-service measurements? Vehicle miles traveled per day? Traffic delay? When you walked down the street to ask your friend to come out and play when you were 8, none of this mattered. It still doesn’t. We just pretend it does.

Not only do we get safer cities with design-oriented approaches, we get more livable streets, more transportation equity, and nicer neighborhoods. While certain cities “get” this approach and progressive agencies are doing great work, the national culture is dominated by acquiescence concerning street design – an issue that is at least partially responsible for 35,000 fatalities a year. The dialog needs to change from, “Sometimes auto accidents just happen” to “This is why accidents happen and here is how we change our streets to prevent them.”


Additional Reading:
Journal of Injury Prevention: Safety in numbers: more walkers and bicyclists, safer walking and bicycling, 2003.
The New Yorker: Wrong Turn: How the fight to make America’s highways safer went off course., 2001
London Cyclist Magazine: Dutch Campaigners explain why the Netherlands is now so bike friendly


Friday Reading

The Tissue of Straight Lines: a meditation on NYC’s grid street network from Kneeling Bus, one of the few blogs I read which leaves me saying, “I wish this guy wrote more articles.”

The grid that originated in 1811 will never be finished as long as it remains in place, because it will never stop challenging its inhabitants to infuse its neutral, rectangular blocks with the vibrant content of humanity and culture.

Designs For Working: Malcolm Gladwell on Jane Jacobs and how her ideas have been co-opted by corporations looking for collaborative, social working environments. See: Zappos’ plan for Las Vegas.


Sparely populated suburbs may look appealing, she said, but without an active sidewalk life, without the frequent, serendipitous interactions of many different people, “there is no public acquaintanceship, no foundation of public trust, no cross-connections with the necessary people–and no practice or ease in applying the most ordinary techniques of city public life at lowly levels.”

“The Solomon Curve, developed in 1964, states that those driving slowest will be at the greatest risk of crashing. This outdated model, which ignores pedestrian safety entirely, still guides traffic engineering toward higher speeds.” StreetsBlog

This has been going around like wild fire. The 85th Percentile Rule in Traffic Engineering from Copenhagenize: an outdated way of setting traffic speeds which ignores neighborhood context, pedestrians and cyclists. This model is still being used in almost every city in the world.

Imagine a street where the average speed is 50 km/h. If the speed limit is reduced by 5 km/h then, according to this archaic model, the drivers are allegedly exposed to a higher risk. What is most shocking is that this entire concept completely ignores pedestrians and cyclists. Another horrific conclusion from this graph is that when you increase the speed limit, the crash risk is alleged to be less than for slow speeds.

The Institute of Traffic Engineers wrote: “The 85th Percentile is how drivers vote with their feet”. They forgot to mention that, when it comes to establishing speed limits in cities, pedestrians and cyclists are excluded from this election. They don’t even get the chance to go to the polls.

All this right now in 2012. In your street. With your tax money.

And finally, the benefits of preserving local manufacturing districts. Proximity is Creativity: Unlocking the Value of the Garment District from Urban Omnibus. There are some things China just can’t do.

Let’s say it’s your last year at school, and you have a set of starter designs that are very marketable. What happens next? You need to get someone to make your production patterns; you need to able to source fabrics; you need to be able to sell, to have access to the stores. So let’s say you come up with a 20-piece order. You can go out into the Garment District, find a cutting room or a sewing room, and have your 20 pieces produced and shipped to a store. You can’t get only 20 pieces made in China, not today, not ever. That is what validates what goes on in the District today: the capacity to produce short runs, samples made with a quick turnaround time.


Are Urban Arterials and Pedestrian Safety Mutually Exclusive?

Pedestrian Traffic Accidents, 2007-2010. What interesting things stand out?

While looking at a pedestrian traffic accident map for Baltimore the other day, one obvious thing stood out;   injuries and fatalities are collected around arterial streets. Besides the obvious reasons for caring about this issue, pedestrian crashes usually make up the majority of traffic related fatalities, and while a fender bender is often easy to walk away from, pedestrian traffic injuries are often life changing events.

So, for non-transporation planners, urban arterial streets are usually 4 lane roads which accommodate through traffic – usually downtown to suburb commuters. Traffic speeds and volumes tend to be higher on these streets, and while many of Baltimore’s arterials double as neighborhood “Main Streets”, like Greenmount Ave., the character of these corridors often leans towards automobiles rather than comfortable, pedestrian environments. In the suburbs, arterials often connect banausic subdivisions or lame strip malls with little pedestrian activity, so it’s not a problem to design these streets for maximum throughput. In urban areas, there is a greater chance for accidents due to pedestrians, bicycles, transit vehicles, and cars all vying for space on a street designed for rush hour traffic.  Things get messy.

Baltimore is not alone.  NYC’s Pedestrian Safety Report shows that while traffic injuries and fatalities have dropped considerably since 2000, major two-way streets account for 47% of pedestrian fatalities but only 12% of the road network. The report also shows serious pedestrian crashes are about two-thirds more deadly on major street corridors than on smaller local streets. So what is NYC doing about the problem? Recent road diet projects are narrowing streets, reducing the number of traffic lanes, adding bike lanes, and widening sidewalks.  Will gridlock ensue? Probably not. Will the world come to an end?  Probably not. Will angry drivers write Mayor Bloomberg and demand their traffic lanes back? Perhaps, but in the interest of public safety, livable communities, and reasonable-ness, the mayor shouldn’t listen to them.

My favorite design guidelines come from famed planner and engineer John N. LaPlante of T.Y. Lin. I won’t repeat his recommendations, which I laid out here, but traditional methods of traffic engineering and design don’t necessarily apply to urban streets.  Inconveniencing drivers by adding 2 minutes to their trip is a reasonable trade off for improved pedestrian safety, neighborhood character, and the economic development benefits which accrue with increased pedestrian and bicycle accessibility.

The answer to the question posed in the title has been “yes” up until very recently.  The very concept of “arterials” in urban areas also comes into question – who wants to live on or do business on a street primarily designed for rush hour traffic?  With enormous amounts of traffic crash data collected, and complete street and road diet designs becoming more accepted by municipalities throughout the country, we have the tools needed to make significant pedestrian safety gains by focusing on major gateway streets.


The Power of Prevention and Innovation in Transportation Safety

Alexandra Rojas Lopera, director of The Fondo de Prevencion Vial

My schedule for this year’s Transportation Research Board Annual Conference was a bit different than last year. Instead of going to  high-profile, big name sessions, I wanted to see how less obvious and more diffuse initiatives were changing transportation policy and improving lives.

Greig Craft started the Asia Injury Prevention Foundation in 1999 as a way to reduce road crash fatalities and injuries in Asia and Africa. Both continents have a huge segment of their populations riding motorcycles, bicycles, and other motorized non-automobile vehicles. There’s also an epidemic of not wearing helmets in these parts of the world based on social norms and misinformation.

Craft, with the The Global Helmet Vaccine Initiative, redesigned helmets so they would fit children better and be cooler in tropical climates.  Profits go back into the community for marketing and road safety education. The program is spreading worldwide, with a UN Resolution calling for a 50 percent reduction in road traffic fatalities by 2020 and signed by more than 90 countries.

 The Fondo de Prevencion Vial, directed by Alexandra Rojas Lopera,  is an outreach and enforcement campaign in Columbia to get roadway users to obey traffic laws. Unlike most countries where the majority of traffic accidents take place in rural and suburban areas, Columbia sees a disproportionate share of traffic accidents in cities due to lax enforcement and a culture of reckless driving and pedestrian behavior. Research has shown that positive marketing campaigns are more effective than fear-mongering. Instead of talking down to the public, the campaign encourages them to be smart, responsible, and avoid excuses for reckless behavior.

Because the number of injuries and fatalities prevented due to these programs is difficult to measure, prevention efforts and the people behind them don’t usually get the recognition they deserve.  As discussed in the book, “The Black Swan: The Impact of the Highly Improbable” by Taleb, if someone led the charge to allow firearms in cockpits before 9/11, nobody would write a history book about this person preventing the U.S. terrorist attacks. There is no way we would have known this policy was directly responsible for preventing hijackings. Their name would be a footnote in the infinite encyclopedia of history.

Likewise, these traffic safety efforts are attempting to change dangerous habits deeply rooted in culture. It’s not enough to just provide helmets or tell people to drive safely.  In Roger’s “Diffusion of Innovation”, the spread of products and new ideas has to be culturally sensitive, reach the right opinion leaders, and have a critical mass to become wide spread enough to make a difference:

Within the rate of adoption there is a point at which an innovation reaches critical mass. This is a point in time within the adoption curve that enough individuals have adopted an innovation in order that the continued adoption of the innovation is self-sustaining. In describing how an innovation reaches critical mass, Rogers outlines several strategies in order to help an innovation reach this stage. These strategies are: have an innovation adopted by a highly respected individual within a social network, creating an instinctive desire for a specific innovation. Inject an innovation into a group of individuals who would readily use an innovation, and provide positive reactions and benefits for early adopters of an innovation.

The hope is to turn authority led innovation into collective innovation decisions. Seeing all of your friends wear a helmet is a more powerful message than seeing a poster telling you to wear one.  Getting positive information out to the public in the right way, to the right people, and in the right format is just as important as building new infrastructure when it comes to public health and safety.