jackson gateway interstate access study · 5/6/2011  · examine i-95 access conditions in jackson...

May 2012

Jackson Gateway Interstate Access Study

Project Update

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Project Overview

Examine I-95 access conditions in Jackson Gateway area of Spotsylvania County

Identify potential for modifications to mitigate existing and future deficiencies in access

– Modifications to existing I-95 interchanges (Exit 118 and 126)

– New interstate access

Prepare Interchange Justification or Modification Report, depending on outcome of study

Receive Conditional Access Approval for access modifications

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Exit 126 Spotsylvania

I-95

US 1

US 17

Exit 118 Thornburg

Project Purpose

Advance FAMPO 2035 LRTP recommendations

Support the County’s Comprehensive Plan

Efficiently facilitate (adequate LOS) peak period traffic flows

Reduce congestion on I-95 between Exit 130 and Exit 118

Improve safety at Exit 126

Reduce congestion on US 1 between Exit 126 (US 1) and US 17

Support regional transportation demand management initiatives

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Spotsylvania County Development District Map from County Comprehensive Plan

I-95

US 1

US 17

Exit 126 Spotsylvania

Exit 118 Thornburg

Completed Tasks

Purpose and need

I-95 HOT Lanes white paper

Existing conditions analysis

Existing and future needs assessment

Environmental baseline analysis

Model calibration and validation

2035 baseline forecasts

Future no-build analysis

2035 build forecasts (with interchange & access modifications)

Initial concept development & screening

Secondary concept development & screening

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Potential Extent of I-95 HOT Lanes Project

Ongoing Tasks

Alternatives refinement and analysis (awaiting feedback from project technical committee)

Project documentation (continuing to develop study documentation)

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Interstate Access Concept Drivers

Existing and future traffic volumes

– AM Peak Hour: Northbound on-ramp at Exit 126

– PM Peak Hour: Southbound off-ramp at Exit 126

Significant travel demand patterns

– Between I-95 and US 1 south

– Between I-95 and US 17 east

– Between Southpoint Parkway and I-95

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Significant Constraints

Signalized intersections along US 1 south of I-95

Existing development

– Near US 17 along I-95

– Along US 1 from Hood Drive to US 17

– At Exit 126

Wetlands, streams, and farmlands south of Spotsylvania Parkway along I-95

Wetlands and streams east of I-95 south of Exit 126

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Initial Concepts and Screening

12 Concepts Developed

– Minor reconfiguration of Exit 126

– Major reconfiguration of Exit 126

– Spreading of Exit 126 to add new ramps

– New point of access independent of Exit 126 in the vicinity of Spotsylvania Parkway

Concepts evaluated for “fatal flaws”

– Ability to serve projected demand

– Impacts

– Interstate weaves

5 Alternatives were carried forward for additional study and one new concept was added

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Concepts Advanced - Alternative 1

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Concepts Advanced - Alternative 3

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Concepts Advanced - Alternative 4

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Concepts Advanced - Alternative 11

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Concepts Advanced - Alternative 13

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Concepts Advanced - Alternative 1 with New Interchange (north option)

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Concepts Advanced - Alternative 1 with New Interchange (south option)

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Summary of Evaluation

Alternative 1 – Does not serve projected p.m. peak hour southbound off-ramp demand

– Lowest cost

– Lowest natural environmental impact

– Most significant built environment impact

Alternative 3 – Does not serve projected p.m. peak hour southbound off-ramp demand

– Highest construction cost

– Lowest natural environmental impact

– Most significant built environment impact

Alternative 4 – Partially serves peak hour demands – some congestion

– Second highest construction cost

– Lowest natural environmental impact

– Most significant built environment impact

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Summary of Evaluation

Alternative 11 – Serves projected demand

– Moderate cost

– Potentially high natural environmental impact

– Moderate built environment impact

Alternative 13 – Serves projected demand

– Moderate cost

– Potentially moderate environmental impact

– Low built environment impact

Alternative 1 with New Interchange (north or south) – Serves projected demand

– Moderate cost

– Potentially high natural environmental impact

– Low built environment impact

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Secondary Screening Summary

Operations, cost, and impact evaluated for each

Costs ranged from $225 to $425 million

Alternatives 11, 13, and 1 with a new interchange performed the best when considering all factors (cost/benefit/impact) as well as cost and benefit alone

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Next Steps

Selection of 2 Build alternatives for detailed analysis

– No build (selected already)

– Modify existing interstate access

– New interstate access in combination with modified existing access

Detailed analysis

– More detailed impact assessment (physical and environmental)

– More detailed cost assessment

– Traffic operations analysis

Selection of preferred alternative

– Refinement and documentation

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