We’re All Traffic Experts Now

At the CTS conference yesterday at the University of Minnesota, I was chatting with a traffic engineer who relayed an interesting anecdote. As a traffic engineer, he is used to addressing packed rooms of people, all filled with firmly held convictions on the way things should be done. He was chatting with a colleague, a civil engineer, about whether people ever offered any input at meetings concerning things like sewer systems. The answer was no.

It should be said that I’m of the opinion that, particularly in some local jurisdictions, community residents might actually have a better idea of how to control their streets than engineers working with standardized approaches; and that, too often, streets are merely viewed as sewers of a sort, channels for simply moving as much stuff — i.e., cars — as possible, with insufficient thought for other considerations.

But the engineer also had a quite valid point, which beleaguered traffic engineers face every day at town meetings across America when trying to, say, tout the benefits of a roundabout. Suddenly, there will be a volley of criticism: Those things are dangerous, they will make traffic worse, etc., despite all statistical evidence to the contrary. Of course, people offering these opinions typically never have actual evidence, nor have they studied the problem in depth, and yet they feel comfortable to make diagnoses on engineering problems which it seems they would not feel comfortable doing in any other arena.

I thought of this morning when reading a dispatch on how Kansas City is going to introduce ramp metering to its highways (thanks Bryan).

This, not surprisingly, prompted a letter in the local paper:

Metering entrance ramps to I-435 is a terrible idea (5/13, National/Local, “Engineers turn to ramp meters to ease gridlock”). I travel to Milwaukee several times a year, and they have metered ramps onto I-94. They slow traffic down, especially during rush hour.

The meters back cars up off the ramp onto the streets, which have intersections with stoplights, and no one can go anyplace. Half the time there is plenty of room for cars to merge in on the interstate, but because of the meter you have to stop and wait.

People who live in Milwaukee and drive on the interstates hate them. Each time I drive up there I can’t wait to get back to Kansas City, where we know how to let people get around.

Ramp meters, as I mention in Traffic, are a particular case where the individual windshield perspective of drivers cannot account for the larger flow of the traffic system, with its multitude of variables; user optimality trumps system optimality in the mind of the driver. As one engineer told me, people ask me, why are you stopping me, the highway’s moving? The highway’s moving because we’re stopping you.” But hold on, K.C. engineers, throw out those models, rip up those studies — we’ve got a driver who “travels several times a year to Milwaukee,” where “everybody” hates ramp meters (everybody, except, presumably the people who are moving more smoothly than they would be without them). But there is “room” on the highway for people to enter, this driver notes. “Room,” or “capacity” as engineers might more properly say, is, alas, not the only variable to consider in highway flow, and indeed, squeezing another driver into that “room” might disrupt the flow, pushing the stream past its critical density, plunging the system from a congested synchronous flow into stop-and-go congestion. Of course, some ramp metering schemes do send traffic back up the ramps — but one might also note that those ramps might typically be backed up already, and that in some cases this is actually made worse without ramp meters. And I need hardly point out that one cannot judge the success or failure of a ramp metering scheme simply by judging one on-ramp at any one time — rush-hour traffic on a congested urban system is an incredibly complex array of networks and flows that are well beyond the ability of any one driver to fully intuit what is going on.

This entry was posted on Wednesday, May 20th, 2009 at 9:53 am and is filed under Drivers, Roads, Traffic Engineering, Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.

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Traffic Tom Vanderbilt

How We Drive is the companion blog to Tom Vanderbilt’s New York Times bestselling book, Traffic: Why We Drive the Way We Do (and What It Says About Us), published by Alfred A. Knopf in the U.S. and Canada, Penguin in the U.K, and in languages other than English by a number of other fine publishers worldwide.

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Upcoming Talks

April 9, 2008.
California Office of Traffic Safety Summit
San Francisco, CA.

May 19, 2009
University of Minnesota Center for Transportation Studies
Bloomington, MN

June 23, 2009
Driving Assessment 2009
Big Sky, Montana

June 26, 2009
PRI World Congress
Rotterdam, The Netherlands

June 27, 2009
Day of Architecture
Utrecht, The Netherlands

July 13, 2009
Association of Transportation Safety Information Professionals (ATSIP)
Phoenix, AZ.

August 12-14
Texas Department of Transportation “Save a Life Summit”
San Antonio, Texas

September 2, 2009
Governors Highway Safety Association Annual Meeting
Savannah, Georgia

September 11, 2009
Oregon Transportation Summit
Portland, Oregon

October 8
Honda R&D Americas
Raymond, Ohio

October 10-11
INFORMS Roundtable
San Diego, CA

October 21, 2009
California State University-San Bernardino, Leonard Transportation Center
San Bernardino, CA

November 5
Southern New England Planning Association Planning Conference
Uncasville, Connecticut

January 6
Texas Transportation Forum
Austin, TX

January 19
Yale University
(with Donald Shoup; details to come)

Monday, February 22
Yale University School of Architecture
Eero Saarinen Lecture

Friday, March 19
University of Delaware
Delaware Center for Transportation

April 5-7
University of Utah
Salt Lake City
McMurrin Lectureship

April 19
International Bridge, Tunnel and Turnpike Association (Organization Management Workshop)
Austin, Texas

Monday, April 26
Edmonton Traffic Safety Conference
Edmonton, Canada

Monday, June 7
Canadian Association of Road Safety Professionals
Niagara Falls, Ontario

Wednesday, July 6
Fondo de Prevención Vial
Bogotá, Colombia

Tuesday, August 31
Royal Automobile Club
Perth, Australia

Wednesday, September 1
Australasian Road Safety Conference
Canberra, Australia

Wednesday, September 22

Wisconsin Department of Transportation’s
Traffic Incident Management Enhancement Program
Statewide Conference
Wisconsin Dells, WI

Wednesday, October 20
Rutgers University
Center for Advanced Infrastructure and Transportation
Piscataway, NJ

Tuesday, March 8, 2011
Ontario Injury Prevention Resource Centre
Injury Prevention Forum

Monday, May 2
Idaho Public Driver Education Conference
Boise, Idaho

Tuesday, June 2, 2011
California Association of Cities
Costa Mesa, California

Sunday, August 21, 2011
American Association of Motor Vehicle Administrators
Milwaukee, Wisconsin

Wednesday, October 26, 2011
Attitudes: Iniciativa Social de Audi
Madrid, Spain

April 16, 2012
Institute for Sensible Transport Seminar
Gardens Theatre, QUT
Brisbane, Australia

April 17, 2012
Institute for Sensible Transport Seminar
Centennial Plaza, Sydney
Sydney, Australia

April 19, 2012
Institute for Sensible Transport Seminar
Melbourne Town Hall
Melbourne, Australia

January 30, 2013
University of Minnesota City Engineers Association Meeting
Minneapolis, MN

January 31, 2013
Metropolis and Mobile Life
School of Architecture, University of Toronto

February 22, 2013
ISL Engineering
Edmonton, Canada

March 1, 2013
Australian Road Summit
Melbourne, Australia

May 8, 2013
New York State Association of
Transportation Engineers
Rochester, NY

August 18, 2013 “Ingenuity” Conference
San Francisco, CA

September 26, 2013
TransComm 2013
(Meeting of American Association
of State Highway and Transportation
Officials’ Subcommittee on Transportation
Grand Rapids MI



May 2009

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