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Dear Engineers (Diverging Diamond)

I have been out of the office for a couple of days and apologize that I don't have much time today to weigh in on the entire divering diamond discussion, but I do want to highlight a couple of intelligent criticisms of my video critique from last Monday.

The first criticism of my critique is essentially an argument of context; I've gotten the context wrong and am way off base if I have a expectation that this highway interchange should be like a pedestrian street in the U.K. or Holland. Here are some of those comments collected from various sources:

  • Sorry to state the obvious, but this is a freeway interchange. Designing it to be a pleasant beautiful place to be is about as absurd as expecting a lakefront promenade to move cars at 60 mph.
  • This rebuttal reflects a serious lack of context on Marohn's part. This intersection *is* the intersection of a busy local road and an interstate highway. It is not central Amsterdam. It is not a residential part of Portland. It is the kind of place where there is an expressway, a few gas stations, and maybe a Cracker Barrel. The first three points were to move cars because that is the essence of that intersection. The more realistic criticism would be that they bothered to do anything for bikes and pedestrians. I'm guessing both are pretty rare there.
  • Why are you comparing a freeway interchange in the outskirts of Springfield, Missouri to bikeways in central Amsterdam or streets in´╗┐ urban UK? A fairer comparison would be with an interchange under a similar setting in Europe, the US, or elsewhere.
  • Complaining that foot traffic has to navigate a potentially snow-covered ditch seriously misses the point - if this were someplace where people actually needed to reach and cross the intersection on foot, there'd be sidewalks.

The second criticism of my critique is a lesser-of-all-evils argument; you think this is bad, you should see what it could have been. Some of those comments:

  • Er...you do know this was the best the could retrofit onto the existing bridge, right? It's not a "complete streets" solution by any stretch of the imagination and it shouldn't be viewed that way. On the ones I've worked on, the center channel (and that is the best place to put it) is at least 14' wide. The right shoulder in both directions should be between 8-10' wide and striped as a bike lane. The cross section on this project reflects only what they could fit on the existing bridge. When you account for the fact that they added about 35% more capacity at a low cost and little in the way of new pavement and no work on the bridge, it's pretty remarkable. It was a functional decision. And it's leaps and bounds better for bikes and peds than it was before.
  • Criticizing an interstate highway interchange on the far northern outskirts of a small mid-western city for not looking like central London or Amsterdam seems excessively snobby and snarky. Short of dynamiting one of the two interstate highways through Missouri, I'm not sure how Marohn could have done a better job designing the interchange to be bike and pedestrian friendly.

In response, our good friend and frequent contributor Nate Hood (Twitter) provided these thoughts in an article that ran in the Atlantic Cities.

At the heart of it, I think Marohn is trying to touch on two separate issues: 1) “Checklist planning,” which is to say that developers will add sidewalks or bike paths to hit the ADA and/or Zoning requirement without even considering how it relates to its surround environment. And, 2) Community Investments: While it might not be fair to compare suburban Springfield, MO to Amsterdam. It shows us the stark contrast of how we’ve decided to spend money and invest in our own communities in the United States versus how other places in the world have decided to invest their limited capital resources.

I'll add to Nate's brilliant comment by noting the following:

If you watch the original video that my comments were based off of, the gentlemen giving the tour was touting how pedestrian- and cycling- friendly this interchange was. That is absurd. This interchange is not "friendly" to pedestrians or cyclists. Suggestions that red decorative brick or yellow markings on the sidewalks would make it so are absurd.

If we in the engineering profession can't step back and acknowledge the absurdity of this situation -- the absurdity that mindless adherence to standards has created -- how can we expect to be taken seriously as leaders by a country going through a difficult and painful economic transition?

It is not good enough to simply follow the ASCE and demand ever more money for our profession when we turn around and waste it in spectacular amounts on things that provide no return (in this instance, moving cars a little faster and building expensive pedestrian/bike facilities that will never be widely used because they are despotic and demeaning). If we want to be part of the solution, we need to reorient ourselves away from our obsession with moving cars more efficiently and towards building places of value.

Getting cars from the Quiki-Mart to the WalMart in 45 seconds instead of 60 seconds is not a good enough contribution to society to justify the money our profession is spending. We are fooling ourselves by pretending we are being "innovative" just because we add red brick, some sidewalk treatments and a cycling trench. Realizing that many are acting in this way in response to financial incentive programs that reward "complete streets" designs only adds to my disgust. 

The United States needs great engineers. When are we going to stop being mindless technocrats and go back to being a real profession?

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Reader Comments (17)

" It is not a residential part of Portland. It is the kind of place where there is an expressway, a few gas stations, and maybe a Cracker Barrel"

And interesting comment for two reasons.

The first is that this is a typical commentary of someone looking at a suburban strip and ignoring what is around it. This "expressway" has residential neighborhoods adjacent to it. Presumably those folks might want to walk or bike to the zoo or schools north of the freeway. Likewise, north of the freeway, there are residential neighborhoods adjacent to the freeway that might want to get to the commercial strip south of the freeway.

The second interesting point is that there are several similar situations I can identify in Portland. One would be 122nd Avenue, which like this "expressway" is a suburban four or five lane commercial strip that includes a public library, some restaurants and several car lots. No one in Portland would mistake 122nd Avenue as "pedestrian friendly", but it has bike lanes and sidewalks on both sides of the street. It is designed with the expectation that people who are not in a motor vehicle will actually choose to use the street, and they do.

The assumption of many traffic engineers is that only those forced to walk or bike will do so. So you don't need to make it attractive or even safe. In fact, many traffic engineers believe safety is best accomplished by discouraging people from either walking or biking. I have heard objections from engineers to marking a crosswalk at a major transit stop on the basis that it would encourage people to cross the street. They acknowledged that people would still cross the street, but they didn't want to signal it was safe by marking a crosswalk.

November 10, 2011 | Unregistered CommenterRoss Williams

"despotic and demeaning" is a great way to describe this type of pedestrian accommodation

November 10, 2011 | Unregistered CommenterAlex

Designing it to be a pleasant beautiful place to be is about as absurd as expecting a lakefront promenade to move cars at 60 mph. Isn't that what Lake Shore Drive is, basically? Or the West Side Highway, or the FDR, or Storrow Drive, or any number of lakeside and riverside expressways that cut off the waterfront from the rest of the city? Why is it only absurd not to have the goal of moving as many cars as quickly as possible?

November 10, 2011 | Unregistered Commenteranonymouse

Keep up the good fight. The American engineering profession is in need of some deep soul searching, as evidenced by the soulless environments many engineers are responsible for.

Perhaps I am being too harsh, but I often say now that I believe the American traffic engineering profession is one with blood on it's hands, because of deliberate choices to increase deaths in a community for the sake of benefiting travel times. I realize to some extent this is bowing to political pressures, but no engineer would knowingly build a bridge that would collapse without warning because political leaders wanted to cut corners, so why is it any better for traffic engineers to respond to requests to speed up traffic in populated areas when they know the outcome will kill more people?

November 10, 2011 | Unregistered CommenterGary Kavanagh

Anonymouse--Sure, the goal of maximal throughput is reasonable. But it is not, should not, and cannot be the end-all-be-all goal of a street. Streets aren't just movement spaces; rather, they are public spaces people also happen to move through. By concentrating only on the throughput aspect, we shaft the other multiple meanings of a street: public (shared) space, green space, commercial space, architectural space, etc. etc. The street is one of the dominant factors of spatial organization (along with the local vernacular and a few other things): when the street works as a thoroughgoing public space, it is because it successfully executes the convergence of all these factors; when it fails, because it exemplifies one factor over all others. (Freeways being the only exception; but they are not designed to succeed in an urban fashion; they are only designed for maximal throughput. Once access limitations are lifted, urban elements will still come back into play.)

Successful streets knit their surroundings into a coherent whole we call a neighborhood; failed ones cleave, dispersing structures further and further and further away. Setbacks are a legal cementation of this reality. Surely you have noticed this, examining successful neighborhoods? Or do you honestly believe house farm tract subdivisions are successful "neighborhoods"? I grew up in one. They fail. They are not fit for growing up or growing old in. And I am not the only one who believes this.

November 10, 2011 | Unregistered CommenterSteve

"Freeways being the only exception; but they are not designed to succeed in an urban fashion; they are only designed for maximal throughput."

They aren't really an exception, just an extreme example of design for the singular value of throughput along one corridor. In fact, they create barriers and reduce access in urban areas for the benefit of people who live elsewhere along the corridor.

November 10, 2011 | Unregistered CommenterRoss Williams


Before you condemn any more traffic engineers over crosswalks, you should probably take a look at this study:


There are situations, especially with major arterial's, where marking a crosswalk does indeed create more pedestrian crashes than if you left it unmarked. Unlike your conjecture, this information is based on actual data and facts, collected over time at locations throughout the country. Argue with it at your peril, and at the peril of many others if your a traffic engineer.

And this goes to the heart of the problem illustrated by this post. Engineers, whether they work in the touristy parts of Amsterdam, or in rural Minnesota have to work with things like hard data, studies, constrained budgets, ranked priorities... not to mention existing bridge structures. Saying something is "pedestrian unfriendly" or describing how something makes you feel is by and large, not really useful in this realm. We're not re-decorating your kitchen here; we're using limited public funds competing against many other priorities, trying to maximize safety, economy and vehicle throughfare, while at the same time trying to minimize environmental and cultural impacts at the lowest possible cost. Despite what your mom told you, how you "feel" has little to do with any of that! Secondly, there are any number of things that don't "feel" safe to people that are actually very safe when measured objectively. In fact, its often music to this traffic engineers ears when somebody says just that. I know if I can make things just a little bit uncomfortable (not a lot) then those drivers or pedestrians will focus on what their doing; they'll put down the phone, slow down...whatever. Its also probably why on some roads its objectively better to not mark crosswalks for people.

If words like "pedestrian friendly" are to have any meaning beyond your drive-by youtube analysis, then you've got to tie them to some actual data. Have there been any bike or pedestrian accidents at that DDI? How about vehicle crashes, are they down? Any bikes or peds interviewed?

Armchair cynicism is easy and its cheap; before the internet it was confined to a beer and a bar stool. HTML hasn't made it much prettier.

November 14, 2011 | Unregistered CommenterTE

I think the engineering profession is quite deserving of condemnation. The built environment of most American streets do not preform well financially, in terms of safety, or in many cases even preventing traffic congestion even though that goal is where most of the money is blown. They fail at creating value for a community, they fail the health and safety of a community, they fail at nearly everything except some arcane metrics in a handbook that is completely detached from the reality we live in.

As for the crosswalk thing, yes just arbitrarily tacking on a crosswalk in some environments doesn't work. That is why in environments with people on foot we have to consider safety through the whole street design, not apply the design of a high speed thoroughfare on every damn street.

November 14, 2011 | Unregistered CommenterGary Kavanagh

" There are situations, especially with major arterial's, where marking a crosswalk does indeed create more pedestrian crashes than if you left it unmarked."

Of course there are. Why would that surprise anyone? Motorists don't honor crosswalks and if you put in a crosswalk, pedestrians will use it. Its actually a classic traffic engineer solution to pedestrians. How do we discourage people from walking? No pedestrians, no collisions. It may make it less safe for those forced to walk, but there will be fewer of them and fewer collisions. Thanks for confirming that is the intent.

November 14, 2011 | Unregistered CommenterRoss Williams

Chuck, I usually agree with your viewpoints, you put into words and data into what I've felt for a long time. I lived in suburban Ohio for longer than I'd care to remember, and I wanted out of there badly. I found always being forced into an automobile to go anywhere annoying, frustrating, and unhealthy. I moved to Seattle because among other things our streets are more complete than in suburban Ohio. I didn't use that language at the time, but was thinking more about the transit system. However, transit planners recognize that being able to walk to your final destination comfortably a key toward an effective transit system. Jarett Walker has some great visuals comparing an urban and suburban layout.

Just for comparison, I went back and pulled out the streetview images of an interstate crossing that I might've actually had some desire to walk across back where I used to live. Sadly, I'm not too surprised that this bridge has absolutely no pedestrian facilities. If I was to cross this bridge, I'd be walking on a shoulder intended for automobiles. There are no crosswalks, and there are still the same gentle sloping curves for high speed exits that people complained about in the diverging diamond.

I'll agree with you that this is nowhere near a complete street, that being said it is infinitely closer to a complete street than the images from suburban Ohio, and I'll place a healthy bet that the diverging diamond is also much closer to a complete street than the interchange it replaced. I for one would be happy to cross it, and I'd feel (and likely be!) safer than the facilities in Ohio.

I'll celebrate the steps that MoDOT has taken to push things toward a more complete street. I recognize that they're starting with something less than ideal, and they've done a good job on improving it. There are bits to be improved. The initial pedestrian crossings into the diamond would be safer if it was signalized for pedestrians. I'td be nice if the sidewalks actually went anywhere (although MoDOT's purview probably ends where their sidewalks end, its upto the locale to continue them. I don't expect MoDOT's engineers to turn lead into gold, but if they can make a nice polished pendant out of it, I'll take it.

November 16, 2011 | Unregistered CommenterNicholas Barnard

This is the comment where I quibble...

I think its a bit unfair to criticize the engineer for some of the comments in this video. I see many of his comments, (e.g. the brick, the view point in the middle of the bridge) as running commentary so that he's not silent the whole way. Yeah, the view? it aint great, but it was something he could point out. That faux-brick, he probably had to argue for the extra four bucks that it cost above a plain cement island. Of course its nowhere near as snazzy as actual brick, but it is prettier than plain concrete, and is something that'll be most noticed by pedestrians, and it enhances the view marginally, nothing to phone home about, but if you're already walking through it with your parents, its worth pointing out.

November 16, 2011 | Unregistered CommenterNicholas Barnard

Nick - You're great, and I appreciate your comments. I'm seeing something completely different here and I'm going to try and lay that out next week.

I kind of feel like society (including cyclists) in this case is like a young boy that gets neglected and beaten by their father. They live in a totally warped world. One day the father comes and, instead of beating the young boy, gives him a piece of meat to eat. Well, they are nowhere near living in a functional family, providing basic sustenance is a far cry from nurturing and it does the child little good in the long-term since he's likely to be beaten again tomorrow, but....for one evening at least, things are "better". We can take that as a victory, of sorts.

This diverging diamond has been constructed in a totally warped world. I realize that it is hard for people to see that since it is the world we live in, but it is completely warped. The relationship between the systems we build and the productivity gains they produce is just plain crazy. Why does WalMart even exist in this location to be biked to? Why is traffic stacking up in the first place? What are we trying to accomplish with our transportation system that would make a diverging diamond part of the discussion? We're even not treating the symptom of the problem here. We're treating the symptom of the symptom of the treatment for the symptom of the problem. It is just maddening.

After we get done with the fundraising this week, I'm going to take the time to explain this in a different way that hopefully will allow people to step back and understand that. I get what you're saying -- the lesser of two evils -- but in a more functional U.S. we wouldn't be having the debate at all. And when stuff like this makes us totally broke, we won't debate it then either.


November 16, 2011 | Unregistered CommenterCharles Marohn

Hi Chuck,
Thank you for your quick reply. I get and understand your comment, and I suspect I agree with much of it. I'm looking forward to your entry next week.


November 16, 2011 | Unregistered CommenterNicholas Barnard

Some of the comments concern aesthetics. I'd like to address that. Engineers generally do what they do because it is the least expensive option. Contractors cost a lot. Materials cost a lot. If you want 'pretty' all over, be prepared to pay for it. A lot. If you can't accept that and aren't willing to pay for it, you have no business saying engineers are 'soulless'.

November 18, 2011 | Unregistered CommenterAnon


Yes aesthetics costs money, but if we created communities of value, with more vibrant land use, they will more than pay for their aesthetics. We go cheap on materials and design, because our land use in America is often such a meager return on investment.

November 18, 2011 | Unregistered CommenterGary Kavanagh

"Engineers generally do what they do because it is the least expensive option"

Four lanes are "less expensive" than two. Wide lanes are "less expensive" than narrow lanes? Running roads over hills is 'less expensive" than smoothing them out with cuts? Right of way is "less expensive" if you cut down all the trees?

The question is not whether something is less expensive, its whether traffic speeds trump all other values. If you start with that assumption, then there is never money left over for "aesthetics'.

November 18, 2011 | Unregistered CommenterRoss Williams

oops. That should read:

"Four lanes are "less expensive" than two? Wide lanes are "less expensive" than narrow lanes? Smoothing out roads with cuts is 'less expensive" than running them over a hill? Right of way is "less expensive" if you cut down all the trees?"

November 18, 2011 | Unregistered CommenterRoss Williams
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