Monday, April 15, 2013

A Response to "Rethinking Traffic Congestion" by Brian Taylor

In “Rethinking Traffic Congestion,” Brian Taylor presents a challenge to the conventional mindset that congestion can, and should, be fought.  I found the ten propositions presented to be very thought-provoking.  That being said, I feel that many of the individual points were misleading.  Taylor is too dismissive of alternative transportation modes and does not give enough weight to the negative externalities of automotive congestion.  And while Taylor’s conclusion admits that there are many ways to fight congestion, the attitude of pessimistic inescapability questions if there’s even value in trying.

Taylor’s premise that congestion is an inevitable companion to economic success does not mean we must resign ourselves to embracing congestion’s negative effects, nor can we neglect the responsibility of a city to provide essential services to the public as best it can.  While there must be at least one business that has relocated away from LA to escape traffic, there’s certainly none that have moved there for the pleasure of being stuck in traffic.

Overall, Taylor identifies many thought-provoking elements of the complex phenomenon of congestion.  With so much funding dependent on the premise of fighting congestion, Taylor has given planners much to think about.

PROPOSITION ONE: Traffic congestion is evidence of social and economic vitality; empty streets and roads are signs of failure.

This is perhaps the most important of Taylor’s points, and there are really two ideas here.  The first is that, fundamentally, congestion is an indicator of the popularity of the route and the destinations it connects. The second is that conventional “costs” attributed to congestion should be balanced with the “benefits” of economic and social vitality.  I agree that congestion is partially an indication of a city’s vitality, and that the costs of congestion are often exaggerated when compared to some ideal but unattainable state of traffic.

While Taylor identifies that causality flows from popularity to congestion, there are many other causes of congestion as well.  Land use patterns (“dumb sprawl”), network design, and roadway management all contribute to delay and unreliable traffic flow.  Efforts to reduce congestion that preserve accessibility, be it through transit or management or compact development or robot cars, still reduce the costs of congestion without reducing the benefits of popularity.

PROPOSITION TWO: Our current focus on transportation networks is misplaced and ignores the effects of congestion on individuals and firms.

Taylor is correct to point out that freeways should not be the sole focus of anti-congestion efforts, as much of a typical trip is non-freeway travel.  But, congestion is a problem on local/collector/arterial streets as well as freeways.  To me, this observation suggests that we should broaden our conception of congestion and the transportation network, not that we should accept congestion as an insignificant component of travel.

PROPOSITION THREE: Automobiles are central to metropolitan life, and efforts to manage congestion must accept this fact.

The utility of private cars, especially in the inaccurate marketplace we have now, is undeniable.  But even with the costs of auto travel internalized, this utility will remain. Experience shows that drivers adapt to pricing, in line with the utility Taylor identifies.  However, Taylor goes on to use auto dominance to dismiss the notion that expanding transportation options can reduce congestion. This defeatist mindset becomes a self-fulfilling prophecy.

PROPOSITION FOUR: Short-lived congestion relief through capacity expansion is not proof that adding capacity is a bad idea.
PROPOSITION FIVE: The effects of latent/induced demand are not confined to capacity expansion.

Here, Taylor attempts to simultaneously promote auto-focused roadway expansion while downplaying multi-modal capacity expansion.  He concedes that expanding freeways does little to meaningfully reduce congestion, since the capacity is quickly filled from latent demand.  He goes on to claim that the increase in accessibility is still a benefit.  I disagree that there is a meaningful increase in accessibility, especially if capacity is added to an already existing route. Moreover, it is still inaccurate to promote capacity addition by claiming congestion or air quality benefits - a claim that is frequently made.

Taylor goes on to point out that effective capacity expansion via other methods, such as better management or multi-modal service, is also subject to the re-filling effects of latent demand.   This is a great point, and one that is not often acknowledged.  However, these capacity increases are usually much less costly, environmentally damaging, and generally have less negative externalities than adding lane-miles to roadways. Additionally, expanding the capacity or performance of multi-modal options has beneficial effects on the transportation market landscape in a way that more lane-miles doesn’t.

PROPOSITION SIX: Changing land use patterns in an attempt to change travel behavior is a very long-term endeavor.

Absolutely true, and it’s good to keep in mind when promoting land use changes.  But even slow changes have to start sometime.  And while regional effects will take a long time to materialize, local changes to land use happen constantly.

PROPOSITION SEVEN: Compact development is correlated with more walking and transit use, but the nature of this relationship is not completely understood.

It is true that correlation is not causation, and is always important to keep in mind.  But even if circumstances make causality difficult to discern, there is causation somewhere.  Research and real-world experimentation are necessary to discover the underlying relationships.  That being said, I absolutely appreciate Taylor’s sentiment.  The relationship between urban form, sociodemographics, economics, and travel are complex and do not simply reduce down to “denser is better.”  Even if the exact relationships are not yet clear, it’s important that we acknowledge that these factors do affect travel in some way, and that we design mindfully.

PROPOSITION EIGHT: The best way to get more people to walk and ride transit is by making driving slow, uncertain, and expensive.

This is, again, a wonderfully radical way to think about congestion.  But this would be a very hard sell to the public as a way of increasing transit and active transportation use.  There’s a case to be made that as urban designers, we should be focused on helping to increase access and expand mobility options by enhancing the performance of alternatives.  Moreover, even the slowest, most uncertain, and expensive driving network does not help increase transit without a good transit system in place to begin with.  Additionally, most transit in America uses the same roads as drivers and must deal with the same congestion.

PROPOSITION NINE: Compact development—whether in older, central city areas, or in newer, outlying areas—increases congestion.

This is my favorite of Taylor’s propositions, and is strongly related to the seventh and eighth propositions.  It is both intuitive and counter-intuitive.  It reminds me that compact development, on it’s own, does not fight congestion.  It’s also worth remembering that fighting congestion, on it’s own, is not the only proposed benefit to compact development.

That being said, the measure of “travel distance per residential acre” is novel and pretty worldview-altering, in my opinion.  I’ve always thought about trip reduction on a per-trip distance basis, but this is different.
“Put simply, vehicle travel decreases more slowly than population density increases, and congestion is the result.”
This is a very astute observation.  However, many of the policy approaches for reducing congestion: better transportation alternatives, better land use mixes, etc. aim to reduce vehicle travel (while maintaining overall accessibility) and become more feasible as population density increases.  Thereby addressing both sides of the “congestion” equation.

PROPOSITION TEN: Absent some form of congestion/parking pricing, development patterns congruent with private vehicle use offer the best chance for land use planning to reduce congestion.

Absolutely, we must design in harmony with private vehicles – but that does not mean a blind pursuit of their every need, nor does it mean neglecting alternatives.


Taken together, Taylor’s propositions present a dramatic rethinking of the role of congestion in the complex system that is the transportation network. Though I take issue with some of Taylor’s assertions, I appreciate the article’s effort to broaden the discussion around a topic that is often approached single-mindedly and receives little critical thought.

Thanks to John Dornoff for editing this post. 

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