Energy, the only E that matters

This discussion responds to the fantastic paper “The Safe Systems Pyramid: A new framework for traffic safety,” by David Ederer, Rachael Thompson Panik, Nisha Botchwey, and Kari Watkins. The paper describes a safe systems program based on those used in public health. My aim is to apply the ideas in the paper to my experiences in the industry. Safe Systems thinking is gaining a foothold in the USA. We have an opportunity to get it right, not simply add another E.

The tiers of intervention

In a nutshell, the paper discards a century of traffic safety practices in the United States, especially the prevailing 3E system (engineering, education, enforcement). As a substitute it posits a safe systems program based on those used in public health. These approaches gauge interventions from requiring more individual effort to having a larger population health impact. For example, brushing your teeth with fluoride toothpaste requires individual decision-making. Adding fluoride to drinking water extends the benefit to all.

The paper applies “the Safe Systems Pyramid to a hypothetical Vision Zero program, highlighting how the framework can be used to prioritize efforts using a Safe Systems approach.” It includes the table and image below, which groups example interventions to five tiers. This is my departure point.

Isolate vehicle-specific interventions

The idea behind this blog is to apply the ideas in the paper to my experiences in the industry. Let me start by isolating vehicle-specific interventions. Planners and engineers do not really involve themselves with driver’s licenses, seat belts, helmet, and automatic braking systems. Maybe they should, but these are mostly the province of manufacturers and regulators. They are not really in design guides and planning policy documents. DMV, not DOT.

One vehicle element that does play into street design and operations is vehicle size. As vehicles have gotten larger over the years, the size of parking spaces have grown. In urban spaces where street design is a game of inches, cities must resist the pressure to accommodate Hummers.

Below I have isolated the vehicle-specific interventions.

Tier 5: none listed
Tier 4: forward, rear, and side collision warning; seat belts; helmets; vehicle standards requiring safety features
Tier 3: air bags; automated emergency braking systems; speed governors; alcohol ignition interlocks; vehicle standards requiring the installation of latent safety features
Tier 2: none listed
Tier 1: safety features on commercial fleets

Relabel

Next, I want to re-consider the Approach to Prevention names and groupings. I try to align the terms with current industry practices.

Tier 5

I’ve always had an issue with the term “education” as it relates to traffic safety. The paper quotes Thomas Frieden: “The need to urge behavioral change is symptomatic of failure to establish contexts in which healthy choices are default actions.” [1] I often refer to this quote from Clay McShane: “It is instructive to remember that streets used to be different than they are today. Modern ‘improvements’ were not universally embraced when they were first put in place…in the 1920s and 1930s pedestrians had to be trained to cross at intersections and wait at traffic signals.” [2]

Conversely, I remember “Fireman Box” visiting my elementary school to talk about fire safety education. Don’t play with matches and so forth. The difference is that fire is an inanimate object. Traffic safety was always an effort to remake the world for drivers. Spend some time with Peter Norton’s book if you want to know more.[3]

In an effort to extricate ourselves from alliterative Es, let us relabel education social marketing. Let us focus on societal changes, similar to vaccination and recycling campaigns. And let us target drivers, as they have the potential, inadvertently or not, to do the most harm. A good analogy is Home Zones.[4] The focus is driver behavior, it is expected for children to be in and around the street, and drivers are considered at fault by default.

Tiers 3 & 4

Active and latent safety measures fall under the Traffic Operations rubric. This is the world of the PTOE.[5] The “active” measures rely on driver behavior. A stop sign is only as good as the number of drivers who stop. The “latent” measures, like Ped Head Starts (leading pedestrian intervals) are more automatic. It’s easy to yield to the person in the crosswalk if you still have a red light.

I often need to remind myself of certain definitions. My computer dictionary defines latent as, “Physiology…present in the body without causing disease, but capable of doing so at a later stage, or when transmitted to another body.” Things that are there, but not doing anything yet. A speed governor is latent because it only acts if the speed reaches the limit.

To Traffic Operations I would add red light and speed cameras. I realize these are seen as enforcement, and they may be regulated by others, but they certainly affect traffic ops. Experience shows large crash reductions, which suggests driver behavior is being moderated.[6]

I would also add a policy on right turn on red. RTOR has a curious history in the USA. It was originally intended to save gas during the oil crises of the 1970’s as fewer drivers would queue at red lights. But like most efforts to ease traffic flow, it mostly induced traffic. It is a real problem for cyclists and people with low or no sight. Recent research documented a 97 percent reduction in vehicle-vehicle conflicts during the red interval after turns on red were removed.[7]. 97 percent is a huge number. That RTOR is still allowed calls into question the traffic industry’s priorities.

Tier 2

The Built Environment interventions are mostly physical measures – traffic calming, traffic separation, etc. This is a subset of what is known as Geometrics, aka Highway Engineering and Street Design. These are things that the traffic profession does to make roads safe (or not).

Tier 1

I find the term Socioeconomic Factors broad and laden with subtext. I would focus on that portion of the industry concerned with the design and shape of our habitats: the built environment. Planners (city, land use, transportation), site designers, environmental engineers, housing policy. I would venture to say that this group of professionals is rarely involved in traffic safety discussions. We need to bring them in.

Below are my suggestions for tier labels.

Tier 5: social marketing (education)
Tier 4: traffic operations (active safety measures)
Tier 3: automated traffic operations (latent safety measures)
Tier 2: highway engineering, street design (built environment)
Tier 1: urban planning, urban design (socioeconomic factors)

Interventions by practice

As a third step, I would parse the programs and interventions by traditional traffic safety and “other”. This highlights the programs and interventions not traditionally the purview of the traffic safety industry. If you are reading this blog, you are probably in the traffic safety industry. But there are other professionals whose decisions affect traffic safety.

Below I separate the non-vehicle specific interventions by practice.

Tier 5: social marketing
- Traditional traffic safety - slow down campaigns
- Other - driver education programs; driver’s education requirement for licensing
Tier 4: traffic operations
- Traditional traffic safety - signals and signs indicating that one should stop or yield; standards and guidance on where to place signs and signals
- Other - none listed
Tier 3: automated traffic operations
- Traditional traffic safety - Signal timing that encourages slower traffic progression; Leading pedestrian intervals; Standards and guidance on signal placement and cycle length
- Other - none listed
Tier 2: highway engineering, street design
- Traditional traffic safety - roundabouts; speed humps; chicanes; raised crosswalks; bicycle infrastructure; design guidance that emphasizes safety over capacity; sidewalks
- Other - sidewalk ordinances
Tier 1: urban planning, urban design
- Traditional traffic safety - none listed
- Other - affordable housing near transit; zoning reforms that reduces vehicle miles traveled; zoning policies; housing policy; occupational safety policy

Removing energy from the network

I want to turn to perhaps the most intriguing point in the paper: energy, the only E that matters. Traffic safety generally focuses on making travel (or traffic) as safe as it can be. It accepts travel as a given. Whose job is it to question travel? Who designs systems that limit travel? Who shifts travel to safer modes? Whose job is it to remove energy from the network?

A few examples. Travelling on a fixed guideway system (train) is safer than travelling on an unfixed guideway system (road) by definition. Train travel is about 17 times safer per passenger mile than driving.[8] Tele-commuting is safer than commuting, by definition. Compact cities have fewer traffic deaths than suburban sprawl, by a number of measures.

Let’s consider a network of streets. [I tend to think about streets as networks, not corridors. This is probably because I am interested in cities, not highways.] On one extreme we have stroads which dangerously twin throughput and access. There is a large amount of latent energy. On the other, we have a series of paths, like on a college campus. There is a small amount of latent energy.

There are a number of ways to remove energy from our hypothetical network of streets. One is speed management. Same number of trips and vehicles, just slower. Another is mode choice. Cycling instead of driving, for example. There is less latent energy in a bicycle than a car. Another is proximity. I grew up 1.5 blocks from the grade school and park. Walking was the obvious choice.

I want to explore the idea of mode choice. I would say that the public largely believes that driving is safe, especially when compared to walking or cycling. Driving also is considered more “secure” than transit. Cocooned in your car, you have to engage with fewer unsavory characters. Suggesting walking or taking the bus instead of driving generally encounters ingrained opposition.

I suppose that driving with seatbelts, airbags, roll cages, and anti-lock brakes is safer than walking on the side of the road at night with no sidewalks. On an individual level. But on a societal level, if everyone walked, everyone would be safer. Safety in Numbers bears this out. If the number of people walking and/or cycling doubles, the number of related injuries increases by only 41 percent.[9]

I confess I know not how to flip this individual vs. collective switch. Too much psychology. But I do know that if we built places where people could walk, they would. In my work on city comprehensive plans, citizens always rank walkability highly.

What if our network of streets is actually a network of hallways in a building? Office building inhabitants routinely walk down the hall, take the elevator or stairs, and grab a coffee at the café on the ground floor. These are “trips” in a network, but devoid of the energy necessary to send another to the hospital. The same cannot be said for the millions of people queued in a coffee shop drive-thru.

The intervention table, expanded

Below I have re-created the table above and added additional intervention examples (bold). I used the same tiers, but with my labels. I organized the interventions by where they would be applied: in vehicles, on roads, city-wide, and other. [Yes, there is always an other.]

Allow me to state unequivocally that they must be applied equitably. Protecting some via fancy airbags and anti-lock brakes while others bear the brunt of a roll cage when crossing the street with no crosswalk to the bus is an ethical failure.

The first five

While the above may be absolutely fabulous, let’s talk implementation. What are the first five on the safe systems list? What really addresses energy, the only E that matters?

Tier 5: social marketing. Free transit and bike share for people under 25, paid for by auto insurers. Age 25 is the year that rates go down, so it would follow that insurers would want to keep young drivers from behind the wheel.
Tier 4: traffic operations. Latent demand instead of current volumes for pedestrian signal warrants. This is also known as the “you can't determine the need for a bridge by measuring how many people are swimming across the river” approach.[11]
Tier 3: automated traffic operations. Ped head starts, aka leading pedestrian intervals. Also leading bicycle intervals. Research suggests a 13 to 46 percent crash reduction.[12] As Richard Retting once told me, drivers are meant to yield to people in the crosswalk, so why not have signals reinforce that?
Tier 2: highway engineering, street design. Separated bicycle lanes and protected intersections. Research suggests a “reduction in bicycle crashes by as much as 50% when compared to a traditional bicycle lane.”[13]
Tier 1: urban planning, urban design. A network of walking/cycling paths and trails connecting schools, parks, shopping, transit, employment, and homes.[14] This is a palliative to suburban sprawl and stroads.

Postscript

As I was writing this, a new report was released by the Johns Hopkins Bloomberg School of Public Health: Narrowing Travel Lanes Saves Lives. [15] One of my mentors Reid Ewing is the Co-Principal Investigator. And I would be remiss if I did not mention Anne Lusk’s work at Harvard.[16] It is wonderful to see public health institutes tackle road safety.

Thank you

A note of thanks to Tom Bertulius (KTUA Planning and Landscape Architecture) and Alicia Zimmerman (Fox Tuttle Transportation Group) who graciously reviewed and offered sterling insights into this discussion.