Traffic

by Tom Vanderbilt

  three to one: Douglas M. Main, “Parking Spaces Outnumber Drivers 3-to-1, Drive Pollution and Warming,” Purdue University News Service, September 11, 2007.

  Chapter Six: Why More Roads Lead to More Traffic

  during the shutdown: See Jon D. Haveman and David Hummels, California’s Global Gateway: Trends and Issues (San Francisco: Public Policy Institute of California, 2004), p. 62.

  “all right by Friday”: See Richard Clegg, “It’ll Be Alright by Friday: Traffic Response to Capacity Reduction,” Department of Mathematics, University of York.

  “based on those changes”: This equilibrium effect seems to happen even in extreme cases, like the 2005 transit strike in New York City. Suddenly, private vehicles, the only way to get into the city, needed to carry at least four passengers to enter during the peak hours of five a.m. to eleven a.m. The world was basically turned upside down. On the first day of the strike, the number of vehicles entering the Central Business District was down 24 percent. People were no doubt confused, unsure of what traffic would be like, or hoping for a quick end to the strike. By the second day, 21 percent fewer vehicles than normal entered. People began testing the waters or could not stay home from work any longer. And on the third day, the number was down to 13 percent fewer vehicles. The strike ended that day, so there is no way to know if traffic would have returned to normal; but clearly, people were adapting, either coming in much earlier (traffic levels at four a.m. tripled) or later than normal, or suddenly becoming believers in car pools. The numbers come from “2005 Transit Strike: Summary Report,” New York City Department of Transportation, February 2006.

  “for other lines”: This line was quoted in the PBS documentary New York Underground (American Experience).

  like population growth: See Lewis M. Fulton, Robert B. Noland, Daniel J. Meszler, and John V. Thomas, “A Statistical Analysis of Induced Travel Effects in the U.S. Mid-Atlantic Region,” Journal of Transportation and Statistics, vol. 3, no. 1 (2000), pp. 1–14. A study in California found that a 1 percent increase in lane-miles creates an immediate increase in vehicle-miles traveled of 0. 2 percent. See Mark Hansen and Huang Yuanlin, “Road Supply and Traffic in California Urban Areas,” Transportation Research A, vol. 31 (1997), pp. 205–18. Robert B. Noland, a scientist at Imperial College London, has compiled an extensive bibliography of “induced demand” research; it’s available at http://www.vtpi.org/induced_bib.htm.

  on the affected roads: See S. Cairns, S. Atkins, and P. Goodwin, “Disappearing Traffic? The Story So Far,” Municipal Engineer, vol. 151, no. 1 (March 2002), pp. 13–22. There was an interesting example of this phenomenon in New York City. When Christo’s The Gates was on display in New York’s Central Park and the roads that crisscross the park were closed to traffic, the city’s transportation department did find local streets more crowded, for the short time that the art was installed. But commute speeds were not hugely affected, largely, according to the DOT, because of special preparations. It is not difficult to imagine that the DOT could also make preparations for closing the park drive to vehicles permanently. The Gates was a huge draw, of course, so we need to factor in how much of the new traffic volume was from people coming to see the art.

  congestion itself as an evil: Asha Weinstein Agrawal, a professor of urban planning at San Jose State University, has shown, using Boston as a case study, that the notion of exactly why congestion is bad is quite fluid, often depending on the needs of a political class. At the turn of the century, safety and personal travel time were often invoked as reasons to cure what the mayor called the “evils of congestion,” but by the 1920s, arguments usually tended to focus on the negative economic consequences of congestion, including a rise in the cost of living. Why? “The growing emphasis on congestion and the cost of living was most likely a political effort to convince the larger population that congestion-generated delay was a problem for them, too, even if they didn’t directly experience it as auto drivers,” she writes. “Once the subway eliminated the congestion-induced delay experienced by people traveling downtown on the streetcars, proponents of expensive and controversial congestion relief projects like the loop highway needed a new argument to convince the general public that they should support these policies, and the cost-of-living argument filled that role.” See Agrawal, “Congestion as a Cultural Construct: The ‘Congestion Evil’ in Boston in the 1890s and 1920s,” Journal of Transport History, vol. 27, no. 2 (September 2006), pp. 97–113.

  “less crowded roads elsewhere”: Brian D. Taylor, “Rethinking Traffic Congestion,” Access (October, 2002), pp 8–16.

  boosts productivity: Timothy F. Harris and Yannis M. Ioannides, “Productivity and Metropolitan Density,” Dept. of Economics, Tufts University, 2000, http://ase.tufts.edu/econ/papers/200016.pdf.

  the hassles of congestion: Helena Oliviero, “Looking for Love in All the Close Places,” Atlanta Journal Constitution, October 15, 2002, and Katherine Shaver, “On Congested Roads, Love Runs Out of Gas,” Washington Post, June 3, 2002. These citations come from Ted Balaker, Why Mobility Matters to Personal Life, Policy Brief 62 (Washington, D.C.: Reason Foundation, July 2007).

  Brookings Institution: See Anthony Downs, Still Stuck in Traffic: Coping with Peak-Hour Traffic Congestion (Washington, D.C.: Brookings Institution, 2004), p. 27.

  close to $12 billion: This, and the $108 billion figure, come from Gabriel Roth, ed., Street Smart: Competition, Entrepreneurship, and the Future of Roads (New Brunswick: Transaction Publishers, 2006), p. 7.

  since Juvenal’s Rome: Asha Weinstein Agrawal argues that “the essential challenges of traffic congestion are fundamental to urban life, and therefore unlikely to disappear as long as people choose to base their social and economic institutions around the free and frequent interaction that becomes possible in cities and towns.” From “Congestion as a Cultural Construct.”

  Dietrich Braess: Dietrich Braess (translated from the orginal German by A. Nagurney and T. Wakolbinger), “On a Paradox of Traffic Planning,” Transportation Science, vol. 39 (2005), pp. 446–50.

  J. G. Wardrop: J. G. Wardrop, “Some Theoretical Aspects of Road Traffic Research,” Proceedings of the Institute of Civil Engineers, Part II (1952) pp. 325–78.

  total travel time would drop: My example for traffic equilibrium and the Braess paradox was inspired by an article by Brian Hayes, “Coping with Selfishness,” American Scientist, November 2005.

  really makes the head spin: When I asked Anna Nagurney, an expert in networks at the University of Massachusetts at Amherst who helped translate Braess’s paper into English, if Braess’s paradox actually exists in the real world, she said that while he was treating the problem mathematically, there is no reason it could not; she also noted that “Braess even lucked out by picking that [traffic] demand because it lies within a range where the Braess paradox will occur.”

  “selfish routing”: Tim Roughgarden, Selfish Routing and the Price of Anarchy (Cambridge, Mass.: MIT Press, 2005).

  more than $2,000: Aaron Edlin and Pinar Karaca-Mandic, “The Accident Externality from Driving,” U.C. Berkeley Public Law Research Paper No. 130; available at http://ssrn.com/abstract=424244.

  2.3 cents per mile: The original estimate comes from Ken Small and Camilla Kazimi, “On the Costs of Air Pollution from Motor Vehicles,” Journal of Transport Economics and Policy, January 1995, pp. 7–32. The updating to 2005 dollars is from Ian Parry, Margaret Walls, and Winston Harrington, “Automobile Externalities and Policies,” Resources for the Future Discussion Paper No. 06-26, January 2007.

  $10 billion per year: M. A. Delucchi and S.-L. Hsu, “The External Damage Cost of Noise from Motor Vehicles,” Journal of Transportation and Statistics, vol. 1, no. 3 (October 1998), pp. 1–24.

  rates and speeds: William T. Hughes Jr. and C. F. Sirmans, “Traffic Externalities and Single-Family House Prices,” Journal of Regional Science, vol. 32, no. 4 (1992), pp. 487–500.

  prices often rise: After Clematis Street in West Palm Beach, Florida, w
as narrowed and retrofitted with bulb-outs and other traffic-calming measures, property values doubled. See “The Economic Benefits of Walkable Communities,” report published by the Local Government Commission Center for Livable Communities, Sacramento, California.

  and coronary problems: There is a huge literature examining the potential links between traffic and health; for example, see A. J. Venn, S. A. Lewis, M. Cooper, et al., “Living Near a Main Road and the Risk of Wheezing Illness in Children,” American Journal of Respiratory and Critical Care Medicine, vol. 164 (2001), pp. 2177–80. The fact that houses tend to be cheaper near heavy traffic introduces epidemiological uncertainty, however, because in general the lives of people near the road are not the same, in socioeconomic terms, as those of people living on estates well back from the road. Is it living near the road that gives a person health problems, or are the problems due to something else about the lives of people who dwell near the road?

  tendency of birds to breed: Harvard University’s Richard Forman, the dean of the “road ecology” movement, noted in a typical study that bobolinks and other grassland birds in Massachusetts do not breed when their nest sites are close to high-traffic streets (on streets with three thousand or fewer vehicles a day, they do breed). The suggested culprit is noise. See R. T. T. Forman, B. Reineking, and A. M. Hersperger, “Road Traffic and Nearby Grassland Bird Patterns in a Suburbanizing Landscape,” Environmental Management, vol. 29 (2002), pp. 782–800, and R. T. T. Forman, et al., Road Ecology: Science and Solutions (Washington, D.C.: Island Press, 2003). See also J. A. Jaeger, L. Fahrig, and W. Haber, “Reducing Habitat Fragmentation by Roads: A Comparison of Measures and Scales, in Proceedings of the 2005 International Conference on Ecology and Transportation, eds. C. L. Irwin, P. Garrett, and K. P. McDermott (Raleigh: Center for Transportation and the Environment, North Carolina State University, 2006), pp. 13–17.

  less able to afford cars: See Donald Appleyard, M. Sue Gerson, and Mark Lintell, Livable Urban Streets: Managing Auto Traffic in Neighborhoods, a report prepared for the Federal Highway Administration, 1976. Many of Appleyard’s findings were reconfirmed in a study by the New York City group Transportation Alternatives, “Traffic’s Human Toll,” 2006; available at http://www.transalt.org/press/releases/061004trafficshumantoll.htm.

  were taxing the poor: It follows that poorer areas also suffer more exposure to the exhaust of passing traffic. Studies in Leeds, England, for example, found that economically disadvantaged areas had higher levels of nitrogen dioxide. See G. Parkhurst, G. Dudley, G. Lyons, E. Avineri, K. Chatterjee, and D. Holley, “Understanding the Distributional Impacts of Road Pricing,” Department of Transport, United Kingdom, 2006.

  by Garrett Hardin: See Garrett Hardin, The Tragedy of the Commons.” Science, December 13, 1968.

  oft-invoked “tragedy”: Shi-Ling Hsu, “What Is a Tragedy of the Commons? Overfishing and the Campaign Spending Problem,” February 21, 2005, bepress Legal Series, Working Paper 463; http://law.bepress.com/expresso/eps/463.

  any traffic engineer: Gary Toth, a planner with the New Jersey Department of Transportation, told me in a conversation in early 2007: “We ran a calculation this week for the twenty congestion-related projects that I have in my division. Those twenty represent about ten percent of the congestion in New Jersey. The construction cost to fix those is $6.7 billion.” Given that about $100 million of the department’s $600 to $700 million budget can be spent on congestion projects, he said that “at the rate the public is providing funding for us,” he could expect those congestion projects to be completed in 670 years.

  build new ones: See, for example, Joel Kotkin, “Road Work,” Wall Street Journal, August 28, 2007.

  all those fuel taxes: Mark Delucchi of the Institute of Transportation Studies at UC-Davis estimates that current payments in the form of fees and taxes by car users to the federal government fall below the costs the federal government pays for car use by some 20 to 70 cents per gallon of fuel. See Mark A. Delucchi, “Do Motor-Vehicle Users in the US Pay Their Way?” Institute of Transportation Studies, Research Report UCD-ITS-RP-07-17, University of California, Davis, 2007.

  in the 1960s: See “The Gasoline Tax: Should It Rise?” Wall Street Journal, August 18–19, 2007.

  “90 percent of the time”: Martin Wachs, “Fighting Traffic Congestion with Information Technology,” Issues in Science and Technology, vol. 19 (2002), pp. 43–50.

  two Canadian researchers: See K. Mucsi and A. M. Khan, “Effectiveness of Additional Lanes at Signalized Intersections,” Institute of Transportation Engineers Journal, January 2003, pp. 26–30. The authors also note that additions to larger intersections will become congested more quickly than additions to smaller crossroads. They write: “If a one-lane road (per direction) gets saturated at 1,000 vehicles per hour (vph) and annual growth is 3 percent, the additional lane will have an uncongested lifetime of approximately 24 years. If a three-lane road (per direction) gets saturated at 3,000 vph and annual growth again is 3 percent, the uncongested lifetime of the additional lane is only 10 years, even without factoring in the diminishing marginal capacity benefit of the additional lane. The diminishing capacity benefits of additional lanes only speed up the process.”

  the fourth just 385: Engineers, for their part, have responded to the problems of large intersections by building highway-style overpasses, which are not just expensive but can look rather freakish rising out of an otherwise flat suburban environment, or with the so-called continuous-flow intersection, a breathtakingly complex creature that removes the left-turn conflict from the main intersection by having drivers turn left before they get to the actual intersection; this is a bit unnerving for some drivers, as the design makes it seem as if they are headed into the oncoming lane. Early studies, however, have shown that these designs actually move more traffic more safely than conventional intersections. At an intersection in Baton Rouge, Louisiana, wait times were reduced from four minutes to one. For a good roundup of CFI intersections, with animations, visit AMBD Engineering’s Web site at http://www.abmb.com/cfi.htm.

  an estimated 12.7 percent: This number is taken from H. Teng and J. P. Masinick, “An Analysis of the Impact of Rubbernecking on Urban Freeway Traffic,” Center for Transportation Studies, University of Virginia, Report No. UVACTS-15-0-62, 2004, p. 47.

  “it is a bad bargain”: Thomas Schelling, Micromotives and Macrobehavior (New York: W.W. Norton, 2006), p. 125.

  photos of incidents: Melissa Leong, “Best and Worst: Driving GTA’s Highways with Sgt. Cam Woolley,” National Post, July 18, 2007.

  “or other vehicles”: Andrea Glaze and James Ellis, “Pilot Study of Distracted Drivers,” Center for Public Policy, Virginia Commonwealth University, January 2003.

  would have gone up: As a thought experiment, consider that the salad bar was actually free. What would happen? There would be huge queues of people lined up for the free food. As Tim Harford points out, “We recognize that food, clothes, and houses cannot be free or we would have quickly run out of them. It is because roads are free that we have run out of spare road space.” From Harford, The Undercover Economist (Oxford: Oxford University Press, 2004), p. 88.

  more people want to use them?: William Vickrey, “Pricing in Urban and Suburban Transport,” American Economic Review, vol. 53 (1963). Reprinted in Richard Arnott, Kenneth Arrow, Anthony B. Atkinson, and Jacques H. Drèze., eds., Public Economics: William Vickrey (Cambridge: Cambridge University Press, 1994).

  the results to friends: The Vickrey story is taken from a working paper by Ron Harstad at the University of Missouri, available at www.economics.missouri.edu/working-papers/2005/wp0519_harstad.pdf.

  rationalize its loss: For an interesting discussion of these ideas based on laboratory experiments, see Erica Mina Okada and Stephen J. Hoch, “Spending Time Versus Spending Money,” Journal of Consumer Research, vol. 31 (2004), pp. 313–23.

  than on another day: Richard Clegg, “An Empirical Study of Day-to-Day Variability in Driver Travel Behavio
r,” Department of Mathematics, University of York, Heslington. Retrieved at www.richardclegg.org/pubs/rgc_utsg2005.doc.

  dropped by 13 percent: Kitchen, in an e-mail, pointed out that all results are “non-equilibrium.” That is, if the roads were actually tolled, traffic speeds would improve, attracting additional users.

  increase speeds by 50 percent: John D. McKinnon, “Bush Plays Traffic Cop in Budget Request,” Wall Street Journal, February 5, 2007.

  jump by 5 percent: Philip Bagwell, The Transport Revolution (London: Rout-ledge, 1988), p. 375.

  go into buses: As Puget Sound’s Kitchen points out, the revenues generated from economically efficient tolling are greater than the total surplus that is gained through drivers’ saved time, which makes the question of how revenues from pricing get redistributed an important, if often neglected, one.

  thus more popular: For more on this “virtuous circle,” see Kenneth A. Small, “Unnoticed Lessons from London: Road Pricing and Public Transit,” Access, vol. 26 (2005), pp. 10–15.

  show up so often in networks: An interesting example from the traffic world that recalls Laval’s monorail case is Route 29 in Trenton, New Jersey. A product of the 1960s era in which cities elected to build massive high-speed highways through the middles of downtowns or alongside waterways, Route 29 is a dangerous road, with numerous crashes and some two fatalities over a fifteen-year period, as I was told by Gary Toth, an engineer with the New Jersey Department of Transportation. Part of the reason was that cars were “blitzing” down a road that was marked for 45 miles per hour but designed more like a 65-mile-per-hour freeway (with all the standard “safety” provisions of clear zones and the like). Drivers would then inevitably encounter the back of a queue of cars waiting at a signalized intersection; it was a classic “hurry up and wait” situation. Rather than have a bunch of high-speed cars encounter a single light with a long delay, Toth and his colleagues wondered what would happen if Route 29 was converted from a highway into a more aesthetically appropriate and pleasant “urban boulevard,” with a lower speed limit and several more sets of signalized crossings. Wouldn’t that just cause more congestion? Wouldn’t it foist an unconscionable delay upon drivers? When they ran simulations, they found that the new system added only two minutes to the total trip during peak times. Instead of one large queue at a signal, the wait would be redistributed among a set of lights. Importantly, the new system carries the added benefit of being much safer as well, as it involves less sudden braking at high speed.