Archive for April 14th, 2009

Traffic Advisory

Other journalistic engagements have tied me up recently, so apologies for the slow pace of posting, the diminished Level of Service, which should continue a bit longer.

On other fronts, I’m going to shortly begin a not-quite-named transportation-related column for Slate. It will cover essentially any form of getting from point a to point b, from Shinkansen to Unimogs to personal hovercraft to traditional bipedal arrangements. I’d love any suggestions for story ideas (including studies, etc.) at:

Posted on Tuesday, April 14th, 2009 at 5:13 pm by: Tom Vanderbilt
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‘Portion Distortion’ and the American Road

I’ve recently been reading a number of papers by Brian Wansink, director of the Cornell Food and Brand Lab at Cornell University, and author of Mindless Eating.

One of Wansink’s more interesting findings is that the way food is served to us affects how much of it we will eat. He calls this “portion distortion.” Not only does the size of the portion itself affect how much we will eat, but so too does the size of the container it comes on (or in).

This seems to happen even to highly educated health professionals; in one study, he found they ate 31% more ice cream when it was served to them in a larger bowl (with a larger spoon, their consumption went up by more than 12%). In another experiment, people given larger containers of popcorn in a theater ate more than those given smaller containers — even when the popcorn was stale (though the affect was reduced when the popcorn wasn’t fresh — i.e. larger containers boosted consumption by 45.3% with fresh popcorn, and by 33.6% when it was stale). This effect typically seems to happen without people being aware of it.

It’s not difficult to imagine the public health consequences of this, particularly as the American obesity epidemic seems to roughly track a number of changes Wansink has identified in portion size. To wit:

We find portion distortions in supermarkets, where the number of larger sizes has increased 10-fold between 1970 and 2000. We find portion distortions in restaurants, where the jumbo-sized portions are consistently 250% larger than the regular portion. We even find portion distortions in our homes, where the sizes of our bowls and glasses have steadily increased and where the surface area of the averaged dinner plate has increased 36% since 1960. And if our bowls, glasses, and plates do not distort us, our recipes will. In the 2006 edition of the Joy of Cooking, the serving size of some entrées has increased by as much as 62% from some recipes in the first edition of 1920.

One problem (there are others), Wansink suggests, is that the feedback loops begin to fray with larger portion size: The larger the portion size, the less accurate the estimation of calories consumed becomes.

What does this have to do with the road? There is an interesting story in how the rise in portion size — often associated (as Wansink notes) with fast-food restaurants — historically tracks the huge increase in miles traveled (183% growth in per-person miles from 1969 to 2000, a period in which the number of persons itself increased only 41%), which itself is associated with the rise of those same restaurants; not to mention the much-debated work linking obesity to density and travel modes.

But I had a different comparison in mind: The way the size of our roads affects our behavior in “consuming” them as drivers. This was brought home to me again in a recent video made by a group called Park Slope Neighbors, which is working to reduce the size of streets like Brooklyn’s Prospect Park West (a five-lane thoroughfare, two lanes of which are dedicated to parking). As the video below shows, the speeds on the street are routinely in excess of the 30 MPH limit. What makes this particularly worrisome is that across PPW lies Prospect Park itself, and there is thus a steady march of pedestrians (including many children). I’m often struck as a driver by how many people are blowing past me; and, just from personal experience, I see more red-light running on this street than others in NYC.

The one thing I rarely see on PPW is the street used to its full capacity by cars. So in the 90% of the time it’s not hitting that full peak (my own wildly rough estimate, NYC DOT, please feel free to weigh in with actual numbers!), it is treated more like an urban highway, with speeds of 45 (or higher) mph not uncommon.

When I took my U.K. driver’s test in the suburb of Pinner, near London, I was intrigued by how, on several local roads, I often had to pull over to let another driver past, so narrow were the residential streets. This is something I can’t remember ever having had to do at home. In the U.S., talk of narrowing roads often leads to the reflexive question “What about emergency response?” Somehow, England manages to have these roads without suffering from a rash of people dying in house fires (needless to say their traffic safety record is better as well; as a friend who did some consulting for the Department for Transport recently told me, somewhat amazed, ‘they actually seem to really care about reducing the number of people killed on the roads’).

One of the recommendations for Prospect Park West is to put it on a “road diet,” a deeply suggestive phrase in light of Wansink’s research. A separated bike lane would be a great place to start — and would reduce the frequent cases of cyclists using the adjacent sidewalk. But something has to be done to change the context of the street. Underutilized by cars much of the time, it is an inefficient use of urban space, and its capaciousness sends a set of powerful signals to the driver, more powerful than whatever speed limit signs may be present. It represents, to paraphrase Wansink, “mindless speeding.” People drive fast because it feels like they should. They see a wide road, and don’t give themselves much time to see anything else.

And to return to that notion of feedback loops. Wansink noted that with larger portion sizes people became less well adept at judging their calorie consumption; I haven’t seen this study (or maybe I have and have forgotten), but I suspect that the higher speed at which one drives, the less able one is to accurately judge one’s speed. Just a theory.

Sure, we could post yet more signage. We could put increased police patrols along the way. We could run expensive ads showing people what happens to pedestrians when struck by vehicles at 20 mph versus 30 mph. But as Wansink writes, in the context of eating, “it is much easier to change a person’s environment than to change their thinking.”

Posted on Tuesday, April 14th, 2009 at 3:58 pm by: Tom Vanderbilt
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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.

Please send tips, news, research papers, links, photos (bad road signs, outrageous bumper stickers, spectacularly awful acts of driving or parking or anything traffic-related), or ideas for my Transport column to me at:

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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



April 2009

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