No New Math from China Traffic Jam

This week provided another opportunity to review the state of progress of demand management for roadway traffic. A spectacular traffic jam outside of Beijing attracted world attention, likely only because it has lasted several days, instead of the more usual hour or two that we now frequently enjoy as a respite from our families while listening to our favorite music.

A WSJ article by Carl Bialik (2010.08.28), The Inconvenient Truth About Traffic Math: Progress Is Slow, opens with “there is absolutely no way congestion can stop increasing” then hauls out a stack of miserable statistics such as “peak-hour trips now average 25% longer than non-peak hour trips, up from 9% longer 25 years earlier”.

Several solution approaches are mentioned, then criticized as ineffective (“tools [such as ramp metering] shaved an average of about three minutes of travel time for each rush-hour commuter, each week”) or rejected outright (“adding roads … lead[s] to more travel, because of an effect … describe[d] as triple convergence. Many drivers who had shifted their trips to off-peak hours, or to different roads, or to public transit, resume their previous pattern and converge onto the new highway”).

Instead, we are “working to spread traffic out more evenly” (which we were told a paragraph before will save me a whopping 3 minutes per week).

The rest of the article completes a litany of disturbing stats and limp solutions – solutions we already know are growing in cost and diminishing in effectiveness. Ominous in its expense and limited effectiveness will be to “merge data from 60 million devices to detect patterns and build a prediction engine…to predict traffic accurately within 20 minutes, at 80% reliability.”

The Montague Street Flyover

Another will “weave together information about multiple modes of transportation, including road and rail, then attempt to shift traffic accordingly [by using] such information to tell drivers, via electronic roadway signs, how long it will take to get to a popular destination by different routes.” Such approaches are intended to “get a lot more use out of our existing transportation infrastructure.”

Well, very little, actually. We know well that these measures all have minor impacts, like the earlier 3-minute-per-week effect. Similar to attempting to cure Alzheimer’s with Ginkgo Biloba, these impacts are swamped by the growth in vehicle miles traveled as populations grow, accumulate wealth, buy cars, abandon transit, and spread out. Cumulatively, all of our increasingly complex smoothing tools and sanding tricks provide only diminishing returns in congestion abatement.

And we all know this.

There is one tool that has proven the exception: road pricing. Done correctly, as in Stockholm, Singapore or on the SR-91, it produces an initial 15-25% traffic reduction, which can then be sustained with market pricing.

So what’s new? Nothing, really. Every one of the people quoted by Bialik in his Times article knows, studies, writes about or sells road pricing as a solution to the problem. So, why no mention of the only known sustainable solution? WSJ editorial policy? Bialik doesn’t like the idea? The solution just slipped everyone’s mind when interviewed by Bialik?

Why do we persist in hoping and praying like this? “Oh Great Transportation Fairy, we pour out our hearts that you will grant us our birth-right of infinite road space. We know you do not listen, but we beseech you anyway.”

As my mother often told me: “The Transportation Fairy helps those who help themselves.”, but as Bialik documents, rather than help ourselves we seem satisfied praying to some pretty minor saints.