Imagine no traffic engineers, it’s easy if you try.

No lines below us
Above us only sky
Imagine all the people
Living for today…

Imagine no transportation planners, it isn’t hard to do.

No homes to relocate
And no forecasts too
Imagine all the people
Living life in peace…

You may say I’m a dreamer
But I’m not the only one
I hope someday you’ll join us
And the world will be as one

Imagine all the people sharing all the roads.

I wonder if you can
No need for speed or violence
A brotherhood of man
Imagine all the people
Sharing all the world…



We conclude that, in the field of public education, the doctrine of “separate but equal” has no place. Separate educational facilities are inherently unequal. Therefore, we hold that the plaintiffs and others similarly situated for whom the actions have been brought are, by reason of the segregation complained of, deprived of the equal protection of the laws guaranteed by the Fourteenth Amendment.  [US Supreme Court]

There was a world before traffic engineers. We should ask “What problems were the traffic engineers trying to solve when the profession was first created?”

The life of urban streets, which was often chaotic without cars, became magnitudes more dangerous with the onslaught of the automobile. The story is now well documented in Peter Norton’s excellent history Fighting Traffic. The solutions worked, to an extent, in that fatality rates have steadily fallen, in part due to traffic engineering (as well as vehicle design and safety features, emergency response, medical care, better driver education, better highway engineering, alcohol regulation, and other factors).

VMT vs. Death per VMT Source:
VMT vs. Death per VMT Source:

But the solutions to one set of problems begets a new set of problems. Now I would probably trade the problems of 1915 for the problems of 2015. The world is a much better and safer place overall. But just because the solution of the traffic engineer is better than the world before, doesn’t mean it is the best possible world.

The profession has locked in on a number of sub-par tools, including AASHTO Green Book, ITE Trip Generation Handbook (critique), the Highway Capacity Manual and Level of Service. [Comment, these books, which should be free, open content, are quite expensive.] While there are those fighting the good fight, that fight is an upstream battle against the status quo.

In the parlance of Twitter #NotAllTrafficEngineers are unthinking technicians following cookie-cutter requirements of standards manuals, but far too many are.

So when I repurpose John Lennon’s Imagine, I, like Lennon, understand the impracticality of the dream (if it were practical, it would not need a song crying for it to be imagined). It would be great if people could safely and efficiently navigate themselves (or have their robots do it for them), without need for the external quite visible guiding hand of the traffic engineer. Clearly modally separate transportation facilities are inherently unequal. And not everything can be equal, but perhaps things should be less unequal.  Shared space is a step in this direction, though most modern shared spaces are engineered, but they are engineered with the idea that travelers (drivers, bikers, walkers) need to interact directly, unmediated by light bulbs and reflective signs.

In short




“Investors want to believe in someone. Forecasters want to earn a living. One of those groups is going to be disappointed. I think you know which.” [Housel, 2014]

There was a world before transportation planners. The problem the new field of transportation planning was trying to solve: Where do you locate facilities, and how wide they should be?

There were roads and railroads built before a transportation planning profession began to profess. Surveyors surveyed. Rail engineers laid ways. Politicos drew lines on maps. Traffic counters forecast. Many roads emerged as deer paths or Indian trails without any conscious design. Cities, counties, and states somehow made roads line up at the border without the need for a higher level of government. Many properties of the general structure of the network can and do emerge organically (like the Hierarchy of Roads). Yet once we want more roads than ancient trails, someone has to decide where to put a new road.

1946 Interstate Highway Plan
1946 Interstate Highway Plan

With the Interstate Highway System, this question became more urgent. The formalization and bureaucratization in the post-World War II era led to transportation planning forming one of the keystones of the rationalist movement. Travel demand forecasting models were designed to size the freeways – roughly should they have two or three lanes in each direction — the logic is best summarized in the phrase “Predict and Provide”. The general system was laid out in 1946, well before computer models, though the specific routes within cities, and the exact rights-of-way took longer.

Because they were publicly provided and largely unpriced, we built more than countries where such roads were private and toll-funded, and as a consequence we drive more than those places. We cannot blame transportation planners for highways slicing cities, that was a decision of mayors representing urban elites — a decision made in ignorance of the consequences (but why would we repeat the error in so many cities?). We can blame them for nurturing zombie lines on maps, contracts with the long dead about future roads never needed that once built induced their own demand and development, making their “need” self-fulfilling. We can blame them for forecasts that were too low for many years and then were/are too high because they failed to understand the structure of demand, socio-economic change, and the potential of technology. We can blame them for thinking one-dimensionally (capacity) about problems that have both supply and demand aspects. We can blame them for justifying and providing the sheen of scientism over the tortuous tracks of civic officials and greed of the growth machine.

#NotAllTransportationPlanners fail to understand the changes that are occurring, and have occurred, but far too many do.


A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King
A Political Economy of Access: Infrastructure, Networks, Cities, and Institutions by David M. Levinson and David A. King


Everything has a design. Not everything has a designer.

Interaction requires rules (tacit or explicit, understood in advance or created on the fly). Not all rules are created by lawyers or legislators or engineers.

The future emerges, it is not centrally planned, it is not (accurately) forecast.

There was a world before modal segregation, before extreme channelization, before standards, before cookie-cutter mass production of road designs.

We cannot return to the past, but we can be informed by it. We can look at things that worked better (like pedestrian travel times in a pre-modally segregated world), and worse (like pedestrian fatalities in a pre-modally segregated world), and see if there are other ways to achieve the optimal mix. It may require a new profession, one that is neither “traffic engineering” nor “transportation planning” in the traditional sense. What would this look like?





With all due respect to John Lennon.