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DOT Ped Safety Claims Based on ’70s Studies

DOT Deputy Commissioner Michael Primeggia on March 15: "I know that two-way streets are less safe."

A couple of weeks ago, following the epic, 650-person "One Way? No Way!" public meeting in Park Slope, Brooklyn Papers columnist Gersh Kuntzman accused his fellow Park Slopers of being "closed-minded, anti-intellectual whiners" for rejecting DOT Deputy Commissioner Michael Primeggia's "logical presentation" claiming that Sixth and Seventh Avenues would be safer for pedestrians if converted to one-way operation.

"Superficially, it would seem that crossing traffic on a one-way street is preferable to crossing a two-way street. As is often the case, the conventional wisdom is wrong." -- Journal of the Institute of Engineers, 2004

But where was the logic? Primeggia held the floor for 45 minutes yet failed to provide data from a single case study to back up his unequivocal safety claim. He offered only one specific example, a 1.5 mile stretch of Glenmore Ave. in East New York where crashes declined after a 1998 one-way conversion. What Primeggia didn't mention is that Glenmore Ave. runs one-way westbound for a few blocks, then eastbound, then west, then east again. This switching back and forth is a classic traffic-calming technique designed to make a street unappealing to thru-traffic.

Later, during an interview, Primeggia referred Kuntzman to a federal report with a brief chapter on one-way streets. Putting aside the fact that federal traffic guidelines tend to be more relevant to sprawling, auto-friendly suburbs than dense, pedestrian-oriented Brooklyn neighborhoods, the section on one-way streets isn't exactly state-of-the-art. It cites two studies, one from 1978, the other, 1973.

Not only is the report out-dated, it actually does not endorse one-ways as the sure-fire pedestrian safety measure that Primeggia claims. "Converting two-way streets to one-way streets," it concludes, "may not be justified solely by pedestrian safety concerns." In fact, "vehicle speeds may increase after conversion from two-way to one-way." (Download the report and see page 96)

So where does New York City's chief traffic engineer get the idea that one-way streets are unquestionably safer for pedestrians? He declined to respond to my questions so I read all of the studies that Primeggia refers to.

The federal report, "A Review of Pedestrian Safety Research in the United States and Abroad," makes clear that vehicles making left turns off of two-way streets are one of the most serious and consistent dangers that pedestrians face. While keeping an eye open for a gap in oncoming traffic, left-turning drivers on two-way streets often fail to see pedestrians moving into the crosswalk on the other side of the street.

The section on one-way street conversions refers to a 1973 study by J.J. Fruin called "Pedestrian Accident Characteristics in a One-Way Grid," a traffic-engineering classic, cited by many other researchers over the years. Fruin observed, "One-way intersections have two conflict sides where the pedestrian must share the green with turning vehicles and two non-conflict sides where the pedestrian has an exclusive green crossing phase." After investigating 32 contiguous one-way intersections in Manhattan over a five-year period, Fruin found that nearly 70% of the pedestrian-vehicle crashes occurred on the two sides of the intersection where vehicles turn into pedestrians -- the "conflict sides."

These are the studies that have informed Primeggia's firmly held belief that one-way street grids are, without question, safer for pedestrians.

However, in the decades since Fruin's study (and Primeggia's coursework at the Polytechnic Institute of Brooklyn), traffic engineers, urban planners and public health experts have developed a more nuanced and holistic understanding of pedestrian safety on one-way street grids. As a 2004 article in the Journal of the Institute of Engineers (PDF) points out, "Superficially, it would seem that crossing traffic on a one-way street is preferable to crossing a two-way street. As is often the case, the conventional wisdom is wrong."

Hundreds of cities and towns across the U.S. are converting their 1950s-era one-ways back into two-ways to reduce speeding, help local business and keep pedestrians -- especially children -- safer. They are doing so because a growing body of research shows that one-way street grids create a number of signficant problems for pedestrians and the city as a whole:

  • One-way street grids force motorists to drive more to get to their destination.
    Rather than simply making one turn and driving half a block, on a one-way street grid drivers often must circle an entire block to get to where they want to go. Not only does this additional driving waste time and gasoline and produce more traffic congestion and carbon emissions, "the increase in the number of turning movements and total miles of travel" makes the street more dangerous for pedestrians too. "There are simply more (typically 30-40 percent) vehicle/pedestrian conflicts within a one-way street network than in a comparable two-way system," according to a 1999 study presented to the Federal Transportation Research Board and the 2004 Institute of Engineers study cited above.
  • One-Way streets tend to encourage faster speeds.
    The federal report that Primeggia himself cites says, "vehicle speeds may increase after conversion from two-way to one-way." But Park Slope residents don't need a study to tell them that. The vehicles careening down one-way Eighth Avenue and Prospect Park West at 40+ mph are the most "logical presentation" anyone needs.
  • Faster one-way streets are more dangerous, especially for children.
    A 2003 study published in the American Journal of Public Health notes, "Higher vehicle speeds are strongly associated with a greater likelihood of crashes involving pedestrians as well as more serious pedestrian injuries." And who gets hurt most on these higher-speed streets? "Children ages 5 to 9 have the highest population-based injury rate in pedestrian-motor vehicle accidents."According to this 2000 study in the Canadian Journal of Public Health, "Children's injury rate was 2.5 times higher on one-way streets than on two-way streets"

Where columnist Gersh Kuntzman saw a neighborhood's "gut emotional reaction" against the "logical presentation" of a blameless DOT "technocrat," I saw more than 650 smart, informed, passionate people who care about their neighborhood come out on March 15 to reject an ill-conceived plan created by a traffic-engineer who was not up-to-date on his own field's research and not interested in hearing about or working to solve a community's very real transportation problems.


1. "A Review of Pedestrian Safety Research in the United States and Abroad," US Dept. of Transportation Federal Highway Administration. B.J. Campbell, Charles Zegeer, Herman Huang, Michael Cynecki. January 2004

2. "A Review of Evidence-Based Traffic Engineering Measures Designed to Reduce Pedestrian-Motor Vehicle Crashes," Richard Retting MS, Susan Ferguson, PhD, and Anne T. McCartt, PhD, American Journal of Public Health, September 2003, Vol. 93, No. 9

3. "A Microscopic Simulation Study of Two-Way Street Network Versus One-Way Street Network," Lum Kit Meng and Soe Thu, Journal of The Institute of Engineers, Singapore, Vol. 44 Issue 2 2004

4. "Downtown Streets: Are We Strangling Ourselves on One-Way Networks?" G. Wade Walker, Walter M. Kulash, and Brian T. McHugh, Transportation Research E-Circular, Number E-C019, December 2000, Urban Street Symposium Conference Proceedings, Dallas, Texas, June 28-30, 1999

5. "Are Child Pedestrians at Increased Risk of Injury on One-Way Compared to Two-Way Streets?" A. Wazana, VL Rynard, P Raina, P Krueger, and LW Chambers, McGill University, Canadian Journal of Public Health, May-June 2000