Will the New Tappan Zee Really Solve I-287’s Traffic Problems?

The New York State Department of Transportation (NYSDOT) and New York State Thruway Authority recently released the Draft Environmental Impact Statement (DEIS) for the Tappan Zee Bridge replacement project. Despite popular demand for better public transit in the I-287 corridor, the project’s DEIS makes few provisions for public transportation in the Lower Hudson Valley. Many residents want a bus rapid transit (BRT) system, and Tri-State has set up a website to advocate for BRT’s place in the project.

This is the third installment of a series of Mobilizing the Region posts that explains why the state is wrong to conclude that the Tappan Zee should be built without bus rapid transit. Today, we examine the DEIS’ analysis of traffic conditions on the bridge and in the I-287 corridor.

The Tappan Zee DEIS' traffic analysis differs significantly from earlier state studies | Photo: Vincent DiSalvio, Journal-News

Traffic has been a serious problem in the I-287 corridor for quite some time. It has been a problem for so long that Governor Pataki formed a task force to study it 15 years ago. The task force’s final report and recommendations essentially kicked off the Tappan Zee Bridge/I-287 Environmental Review process (“Old Project”), which started in 2002 and included hundreds of public hearings and in depth studies. That project was cancelled by Governor Cuomo in October of last year and replaced with the new Tappan Zee Hudson River Crossing Project (“New Project”).

The Old Project’s EIS

The Old Project’s EIS was a comprehensive review of the corridor’s current and future mobility needs, and the 2006 Alternatives Analysis concluded that traffic and mobility would only get worse without transit in the corridor [1]. Specifically:

  • Future traffic levels from projected growth would result in substantially deteriorated traffic conditions and demand that would exceed capacity throughout the corridor.
  • Traffic congestion would spread over more hours, substantially expanding the peak travel periods that are observed today. Critical stretches of roadway in the corridor, including the Tappan Zee Bridge, would experience over-capacity demand in every hour of the morning and afternoon peak periods.
  • Commuters would find it increasingly difficult to adjust their schedules to avoid the growing congestion. With this deterioration of traffic conditions on the thruway, commuters would divert to alternate routes or remain on local arterials longer than they do today. This level of prolonged congestion could impede the future economic and job growth that is projected for the corridor.

The language couldn’t be clearer: “without alternative modes of transportation,” the corridor “would eventually ‘fill up’ with motorists.”

The New Project’s DEIS

Despite using the same traffic model as the Old Project’s EIS, the New Project’s DEIS concludes that traffic would not be a problem if the bridge were built without transit.

For example, the New Project’s DEIS predicts that westbound traffic during the evening commute will decrease between 2017 and 2047. The New Project’s DEIS also seems to say that there will be 1,200 fewer cars per hour on the bridge during the eastbound morning commute than previously expected. This is especially surprising since the Old Project’s EIS analyzed traffic figures for 2025, while the New Project’s DEIS analyzed them for 2047. One would expect that there would be more traffic in 2047 than 2025, not the other way around.

New York State Traffic Projections for the I-287 Corridor

Old Project EIS New Project DEIS
Analysis Year 2025 2047
Traffic Volume 8,800 vehicles/hour 7,668 vehicles/hour

Sources: 2006 Alternatives Analysis, 2011 Draft Environmental Impact Statement

The New Project’s DEIS notes that traffic growth is projected to increase in the I-287 corridor in both the No Build and Preferred Alternative, but the authors do not thoroughly explain how or why the traffic situation will not be as dire as the one projected in the Old Project’s EIS. The New Project’s DEIS analysis asserts that the proposed bridge will increase mobility in the corridor, but this mobility increase will apparently result from fewer accidents and slightly wider lanes on the bridge. Nothing is being done to get vehicles off the road.

The New Project’s DEIS’ conclusions, which differ radically from the state’s previous studies, are vexing. Any person that has read both the Old Project’s EIS’ traffic studies and the New Project’s DEIS’ traffic studies would have difficulty understanding how New York now finds that traffic will not be a problem in the future (especially with no plans to put transit on the bridge).

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[1] Traffic analysis in the corridor is performed using computer models called Paramics and the NYMTC Best Practices Model (BPM). In essence, the process involves inputting data into the BPM – a model that includes 28 counties in New York, New Jersey and Connecticut – and then using Paramics to analyze that data. Transportation data for the BPM was collected through:

  • Surveys of travelers
  • Routine collection operations of NYSDOT and Westchester and Rockland Counties,
  • Reports for other projects,
  • Automatic Traffic Recorder (ATR) counts located at approximately 170 locations, 70 of which were ramps leading to and from I-287, and 100 of which were major intersections within the study area.
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