Mobilizing the Region

Of the two alternatives being studied as part of the Bruckner-Sheridan project (besides the "no build" alternative), the only difference whether the Sheridan remains or is removed.

“We realize that we can’t just look at the highway facility itself; we need to look at the impact of a highway through the community it runs through, it needs to focus on not just moving traffic.” – NYSDOT Region 11 (NYC) Director Phil Eng on the Bruckner-Sheridan Interchange project,  New York Times, July 12.

Few projects demand the type of broad vision described above as much as the Sheridan Expressway in the Bronx. For over a decade, community residents have asked state officials to ease the burden on the South Bronx by removing the 1.25-mile Sheridan and using the footprint for open space and development. But despite Director Eng’s words, last Tuesday’s NYSDOT stakeholder’s meeting on the Bruckner-Sheridan Expressway, the first in 2 years, was a live illustration of an organizational silo at work.

The meeting was convened for the presentation of the Department’s traffic “micro-simulation analysis” results, a process in which future traffic patterns and volumes are projected for each of the project’s alternatives.  Besides a required “no build” alternative, NYSDOT is weighing two “build” alternatives, one which would remove the Sheridan (1E) and one which would keep it (2E).  Aside from the fate of the Sheridan, the two are nearly identical, each creating a new interchange from the Bruckner to direct trucks to the Hunts Point food markets and industrial areas and a new alignment on the Bruckner Expressway to widen a bottleneck over the Bronx River.

Projected to year 2030, the Department sees skyrocketing traffic volumes under any scenario, generally projecting higher volumes on local roads if the Sheridan is removed. These latest results appear quite specific, but need to be taken with a whole shakerful of salt because they are based on the same traffic modeling process and underlying data which the Southern Bronx River Watershed Alliance concluded was “junk science” after hiring Smart Mobility, an impartial out-of-state consultant, to review the state’s data. That 2007 analysis found basic errors, faulty assumptions, and a fundamental mismatch between the project and the traffic model used to analyze it.

Both then and now, the project team used the NYMTC Best Practices Model, or BPM, for studying traffic patterns and projections.  The Department used local traffic counts to calibrate the model, but the BPM’s design and underlying assumptions skew the latest results in the same way as the earlier numbers.

The BPM is a regional model, one which Smart Mobility called useful for analyzing “big picture land use and pricing assumptions.”  However, “it is of more limited use in evaluating the different traffic impacts of the [Bruckner-Sheridan] Build alternatives, because the differences are small relative to the accuracy level of the model. Use of the BPM for screening the alternatives is appropriate, but… the modeling is too coarse to calculate significant differences in future traffic impacts between the alternatives.”  Yet this is precisely what NYSDOT did and presented to the public.

Even if the BPM were an appropriate model to apply to the study area, garbage in still equals garbage out.  Our report also found that “about half of the purported benefits [of keeping the Sheridan] result from model coding errors rather than any real transportation effects.”  These included one-way streets mapped in the wrong direction and ramps coded with incorrect capacity numbers. The BPM also assumes that traffic steadily increases with population, unbounded by physical capacity constraints, producing “an implausibly high level of future traffic in the study area.”  In fact, the magnitude of the projected traffic growth dwarfs the differences between the remaining alternatives.

Because of the model’s uncertain conclusions and the errors underlying the Department’s projections, the decision to remove or retain the Sheridan should be based more on the potential community benefits of each alternative — including, but not dominated by, traffic considerations.  Unfortunately, study of the environmental, recreation, and economic benefits of a Sheridan removal is not part of NYSDOT’s plans.

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