2009
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Jul Documentation for: I–89 Exit 12B ALIGNMENT STUDY
EXISTING CONDITIONS, TRAFFIC ANALYSIS. GEOMETRIC ALTERNATIVES, AND EXPECTED COSTS AND: SUPPLEMENTAL MEMO – ADDITIONAL ALTERNATIVE ANALYSIS
S
N O
TI U L SO
Prepared for the:
S I S Chittenden County Metropolitan ANALY
Planning Organization
Final Report ‐ July 2009 DATA
Prepared for: The Chittenden Country Metropolitan Planning Organization, in cooperation with the Vermont Agency of Transportation, for the Town of Colchester.
This report was funded in part through grant[s] from the Federal Highway Administration [and Federal Transit Administration], U.S. Department of Transportation. The views and opinions of the authors [or agency] expressed herein do not necessarily state or reflect those of the U. S. Department of Transportation.
60 Lake Street, Suite 1E, Burlington, Vermont 05401 TEL 802.383.0118 FAX 802.383.0122 www.rsginc.com
Documentation for: I-89 EXIT 12B ALIGNMENT STUDY
FINAL REPORT EXISTING CONDITIONS, TRAFFIC ANALYSIS, GEOMETRIC ALTERNATIVES, AND EXPECTED COSTS
AND: SUPPLEMENTAL MEMO – ADDITIONAL ALTERNATIVE ANALYSIS
Prepared for the: Chittenden County Metropolitan Planning Organization Final Report - July 2009
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TABLE OF CONTENTS
INTRODUCTION...... 1
PREVIOUS PLANS AND STUDIES ...... 1
PURPOSE & NEED (DRAFT)...... 2
EXISTING CONDITIONS...... 3
PROJECT AREA & LAND USE...... 3
ROADWAY AND BRIDGE...... 4
TRANSIT FACILITIES ...... 4
BICYCLE/PEDESTRIAN FACILITIES ...... 5
UTILITIES...... 5
RIGHT OF WAY (ROW) ...... 6
ENVIRONMENTAL AND CULTURAL RESOURCES ASSESSMENT ...... 6
FLOOD ZONES...... 6
WETLANDS...... 6
STORMWATER...... 6
ARCHAEOLOGICAL RESOURCES...... 6
HAZARDOUS WASTE SITES ...... 7
RARE, THREATENED OR ENDANGERED SPECIES, SIGNIFICANT COMMUNITIES OR DEER WINTERING AREAS ...... 7
TRAFFIC MODELING, NETWORK AND LAND USE ASSUMPTIONS...... 7
OVERVIEW OF CHITTENDEN COUNTY TRANSPORTATION MODEL...... 7
LAND USE ASSUMPTIONS...... 8
HIGHWAY NETWORK ASSUMPTIONS ...... 9
TRAFFIC SCENARIOS ...... 10
PIVOTING ...... 11
OTHER DEVELOPMENT VOLUMES...... 11
VOLUME ADJUSTMENT FACTORS ...... 12
FUTURE SCENARIO TRAFFIC VOLUMES...... 12
SCENARIO VOLUME GRAPHICS ...... 14
EVALUATION METHODOLOGY...... 16
ALTERNATIVES...... 17
TRAFFIC ANALYSIS & LANE REQUIREMENTS...... 20
SIMPLE DIAMOND INTERCHANGE WITH TRAFFIC SIGNALS...... 20
SIMPLE DIAMOND INTERCHANGE WITH ROUNDABOUTS...... 23
MODIFIED DIAMOND INTERCHANGE WITH TRAFFIC SIGNALS...... 24
MODIFIED DIAMOND INTERCHANGE WITH ROUNDABOUTS ...... 26
STANDARD SINGLE POINT URBAN INTERCHANGE ...... 28
MODIFIED SINGLE POINT URBAN INTERCHANGE...... 30
GEOMETRIC OPTIONS SUMMARY...... 32
CONCEPTUAL DESIGN SKETCHES ...... 33
COST ESTIMATES...... 38
SUMMARY OF FINDINGS ...... 38
COORDINATION MEETING WITH VTRANS AND THE AGENCY OF NATURAL RESOURCES ...... 39
LIST OF FIGURES
Figure 1: Project Area ...... 3
Figure 2: CCTA Service in Project Area...... 5
Figure 3: Model Process ...... 8
Figure 4: Circ Highway Segment Map...... 10
Figure 5: Traffic Scenario Volumes at the Study Intersections...... 14
Figure 6: Expected Change in Traffic Due to Tilley / Kimball Connector through O'Brian Property (2018) ..... 15
Figure 7: Simple Diamond with Traffic Signals...... 18
Figure 8: Simple Diamond with Roundabouts ...... 18
Figure 9: Modified Diamond with Traffic Signals ...... 18
Figure 10: Modified Diamond with Roundabouts...... 19
Figure 11: Single Point Urban Interchange ...... 19
Figure 12: Modified Single Point Urban Interchange...... 19
Figure 13: Intersection Geometry - Traffic Signals and Simple Diamond Interchange (2018 PM Scenario) ... 21
Figure 14: Simulation Example of Excessive Queuing Southbound and Westbound at Tilley Drive (2018 Signalized Simple Diamond) ...... 23
Figure 15: Example of 3 roundabouts at an interchange in Brighton, Michigan (photo credit DLZ Michigan Inc.) ...... 24
Figure 16: Modified Diamond Interchange - Traffic Signals...... 25
Figure 17: Intersection Geometry – Modified Diamond Interchange – Roundabouts on VT116...... 27
Figure 18: Intersection Geometry – Modified Diamond Interchange – Roundabout on Tilley Drive ...... 27
Figure 19: Single Point Urban Interchange - Traffic Signals...... 29
Figure 20: Modified Single Point Urban Interchange - Traffic Signals ...... 31
Figure 21: Modified Diamond Interchange – Concept Sketch (Northern Half)...... 34
Figure 22: Modified Diamond Interchange – Concept Sketch (Southern Half) ...... 35
Figure 23: Modified SPUI Interchange – Concept Sketch (Northern Half)...... 36
Figure 24: Modified SPUI Interchange – Concept Sketch (Southern Half)...... 37
LIST OF TABLES
Table 1: LOS Criteria for Intersections ...... 16
Table 2: Simple Diamond Interchange with Traffic Signals - 2018 PM Scenario...... 22
Table 3: Modified Diamond - 2018 Capacity Analysis ...... 26
Table 4: Roundabouts with Modified Diamond Interchange – 2018 PM Peak Hour...... 28
Table 5: Standard SPUI Capacity Analysis - 2018 PM Peak Hour...... 30
Table 6: Modified SPUI Capacity Analysis - 2018 PM Peak Hour...... 32
APPENDIX A – PROJECT MAPS
APPENDIX B – LAND USE ASSUMPTIONS
APPENDIX C – NETWORK ASSUMPTIONS
APPENDIX D – PIVOTING PROCESS METHODOLOGY
APPENDIX E – SCENARIO VOLUME MAPS
APPENDIX F – DESIGN ALTERNATIVES
APPENDIX G – COST ESTIMATES & ASSUMPTIONS
APPENDIX H – DESIGN CRITERIA
APPENDIX I – SUPPLEMENTAL MEMO – ADDITIONAL ALTERNATIVE ANALYSIS
INTRODUCTION The Chittenden County Metropolitan Planning Organization (CCMPO), in association with the City of South Burlington and the Vermont Agency of Transportation (VTrans) is evaluating the feasibility of locating a new interchange on Interstate 89 at VT116, Hinesburg Road in South Burlington. The CCMPO contracted with Resource Systems Group Inc. (RSG) to examine the potential future traffic condition and potential optimal roadway alignments of this interchange (commonly referred to as Exit 12B). A technical committee was formed to review the various stages of the development of this report and included representatives from the City of South Burlington, the Burlington International Airport, VTrans and the CCMPO.
PREVIOUS PLANS AND STUDIES Previous engineering studies which have addressed the possibility constructing a new interchange at Hinesburg Road include: 1) I-89 / Hinesburg Road Northbound Off-Ramp, by Dubois & King. August 1996. This study estimated the potential traffic and necessary geometric alignment of an alternate northbound off-ramp well south (east) of Hinesburg Road which would tie into Tilley Drive on the Pizzagalli subdivision. In addition the study explored the necessary geometry at the intersection of Tilley Drive and Hinesburg Road, specifically addressing whether the Hinesburg Road overpass of I-89 would need widening. 2) I-89 Urban Transportation Improvements, by Dubois & King. October 2003. This study analyzed several potential improvements to the I-89 corridor between Exits 12 and 15, including the Exit 12B interchange. While the study was initiated as an Environmental Assessment, it stopped well short of this and recommendations were made to proceed separately with several individual projects. Traffic projections and environmental screening were performed including potential wetland and archaeological impacts within or near the Interstate right of way (ROW), as well as potential air and noise impacts.
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PURPOSE & NEED (DRAFT) A draft version of a Purpose and Need statement was developed by the project technical committee for this project, as follows:
PURPOSE Provide local and regional mobility and connectivity. In particular, for: ¾ northwest Vermont commuter traffic from Addison County and southern Chittenden County to employment centers in the metropolitan core of South Burlington and Williston; ¾ access to Burlington International Airport and the Vermont Air/Army National Guard facilities; ¾ connectivity between VT Route 116, 15 and U.S. Route 2, and; ¾ access to the South Burlington City Center. Support economic development and employment growth in the region by providing additional mobility options in the metropolitan core. NEED Traffic levels along US 2, particularly at Exit 14 and Dorset Street, have reached capacity during peak times. Numerous safety issues have also been identified in this corridor, particularly at Exit 14. This congestion limits access to the Air /Army National Guard Facilities, the Burlington International Airport and the proposed City Center. South Burlington and Williston are expected to add a combined 3,500 housing units by 2015. Similar increases in employment, commercial activity and airport trips are anticipated within the project area, thereby compounding congestion, as well as safety concerns.
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EXISTING CONDITIONS
PROJECT AREA & LAND USE To the north, Exit 12B would primarily serve the core South Burlington City area (including the planned City Center development – see Figure 1), and to the northeast the Burlington International Airport and Vermont Air and Army National Guard facilities. To the south, the service area includes the well populated and growing Southeast Quadrant of South Burlington and beyond that - the Towns of Shelburne, Charlotte, St. George and Hinesburg. The immediate project area is dominated by existing and planned commercial uses – particularly to the northeast, southeast and southwest. The immediate northwest quadrant includes primarily residential uses, as does Hinesburg Road south of the project area.
Figure 1: Project Area
N
CITY CENTER
EXIT 12B SITE
WILLISTON GROWTH CENTER
TO HINESBURG
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ROADWAY AND BRIDGE For the purpose of this study it is assume that I-89 Exit 12B would connect and access Hinesburg Road (VT 116), an uncurbed two-lane principal urban arterial with 11-12 foot travel lanes and 6-8 foot shoulders. (See Project Area Map in Appendix A). The posted speed limit is 35 mph. The Annual Average Daily Traffic (AADT) here is 7,900 vehicles per day (vpd1). Tilley Drive is new local road, with a curbed width of 30 feet. The existing bridge over I-89 was built in 1963, with two travel lanes and 30 foot curb to curb width. This structure is reported to be in “good to very good condition” according to the latest VTrans inspection report, dated April 19, 2006.
TRANSIT FACILITIES Chittenden County Transportation Authority (CCTA) bus routes serve several portions of the project area (see Figure 2), stopping at County Park apartments on Hinesburg Road just to the north, and in Technology Park on Community Drive. The Montpelier Link Express bus travels on I-89, through the project area.
1 2006, Station D124 (Actual), reported by VTrans Route Log.
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Figure 2: CCTA Service in Project Area
EXIT 12B SITE
BICYCLE/PEDESTRIAN FACILITIES Few pedestrian or bicycle facilities exist in the immediate project area. Long term City plans call for a shared use path adjacent to Hinesburg Road in the project area. An existing sidewalk on Hinesburg Road, leading from Kennedy Drive, ends approximately 1,000 feet north of the bridge over I-89. A shared use path was recently constructed on the north side of Tilley Drive, and plans are in the works to continue this path to Community Drive. (See Constraints Map in Appendix A.) The existing 6-8 foot shoulders on Hinesburg Road are adequate to accommodate on road bicycle use – conforming to the VT Pedestrian and Bicycle Design Manual. The existing Hinesburg Road bridge shoulders do not currently meet these requirements, however.
UTILITIES Utilities in the project area include aerial power and communications lines and buried gas and water mains along the west side of Hinesburg Road. These services continue over and under I-89, however none are supported by the bridge structure. The Pizzagalli subdivision is served by municipal water and sewer, and underground power and communications lines leading from Hinesburg Road.
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RIGHT OF WAY (ROW) ROW widths vary considerably in the project area, and are indicated on the project maps (Appendix A). The Tilley Drive ROW is a consistent 80 feet wide, and reserved ROW areas have been secured for two of the potential interchange ramps (northbound on-ramp, and the alternate northbound off-ramp), which are both 100 feet wide.
ENVIRONMENTAL AND CULTURAL RESOURCES ASSESSMENT All environmental and cultural resource information collected and presented in this report was gathered from previous reports or mapping done by others, including public GIS databases. Known resources have been summarized in the Project Constraints Map in Appendix A.
FLOOD ZONES Flood zone mapping indicates a flood zone on the eastern portion of the Pizzagalli subdivision associated with a tributary to Potash Brook. The planned Tilley Drive extension would cross this flood zone.
WETLANDS Several isolated Class III wetlands, as well as Class II wetlands have been identified in the project area. The wetlands associated with the tributary to Potash Brook have been identified as Class II wetlands by specialist employed during the Pizzagalli subdivision permitting process. Both GIS mapped wetlands (Local, State and National Wetland Inventory Mapping) and wetlands sketched from mapping by others are shown on the Project Constraints Map.
STORMWATER The entire project area is within the watershed of Potash Brook, which is listed as an impaired waterway (ANR DEC 2006 303(d) list).
ARCHAEOLOGICAL RESOURCES The potential for archaeological resources was assessed as part of the I-89 Urban Transportation Improvement Study in 2003, as well as during permit application process for several of the adjoining private properties in the project area. Findings include several areas of interest within the I-89 ROW, a large area on the southwest quadrant of the proposed interchange site (on the Davis Property), as well as several sites on the Pizzagalli subdivision, one of which (at the end of the existing cul-de-sac) has been isolated from disturbance until a Phase III Archaeological site survey is initiated and completed. Archaeologically sensitive areas are shown on the Project Constraints Map from mapping by others.
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HAZARDOUS WASTE SITES No active hazardous waste sites are listed in the latest GIS database from the Vermont Agency of Natural Resources (VT ANR), within the project area.
RARE, THREATENED OR ENDANGERED SPECIES, SIGNIFICANT COMMUNITIES OR DEER WINTERING AREAS No rare, threatened or endangered species, significant natural communities, or deer wintering areas are mapped in the latest GIS database available from the VT ANR, within the project area.
TRAFFIC MODELING, NETWORK AND LAND USE ASSUMPTIONS
OVERVIEW OF CHITTENDEN COUNTY TRANSPORTATION MODEL The Chittenden County Transportation Model (the Model) was used to develop traffic forecasts for the future scenario years 2018 and 2030. The Model estimates the movement of people and vehicles within the region during year 2005 AM and PM peak hours and predicts future traffic volumes based on assumptions about land use and the transportation system. This section provides a brief overview of the Model so the reader has a basic understanding of how key land use change and transportation project assumptions related to this study have been accounted for in the forecasts. Additional information on the model is available on the CCMPO web site at http://www.ccmpo.org/modeling/. For a detailed explanation of the Model refer to “CCMPO Model Documentation”1. The 2005 Model is an update from a model developed by CCMPO in 1998, which was also updated in 2000. The 2005 model is based on updated housing and employment data from the 2005 census and includes a revised network. The Model was also transferred from the ITM/TModel modeling software packages to TransCAD, a transportation modeling and GIS package, in 2000. The Model combines the highway and transit network with land use. The network includes all arterials and significant collectors in the County and some local streets. Road characteristics such as length, functional class, speed limit, number of lanes, and capacity are included. In addition to roadway characteristics, the CCTA fixed route transit system is also coded along the appropriate roads. The Model also includes intersection capacity characteristics such as type of control (traffic signal, coordinated traffic signals, stop, yield, etc), number of turning lanes, and roadway capacity. For the purposes of modeling traffic flow, the Model includes 335 internal Transportation Analysis Zones (TAZs) covering the 18 municipalities in Chittenden County. Traffic entering and exiting the region does so through 17 external zones. Land use is described in terms of dwelling units and employment. Each TAZ includes number of households. Different employment types such as retail,
1 Resource Systems Group, Inc., for the CCMPO, April 2006
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office, industrial, hotel, and school categories are placed into various high, low, or medium trip generation categories. The Model follows the five step process shown in Figure 3 to estimate the location of new development and the resulting AM and PM peak hour travel. The steps are defined as follows: Trip Generation – estimates the number of person trips produced and attracted to each TAZ. Trip Distribution – connects person trips between TAZs. Mode Choice – splits person trips into single occupant vehicles, shared vehicle trips, transit trips, or walk/bike trips. Assignment – Selects the shortest route for each vehicle and transit trip traveling from one TAZ to another based on distance and travel time. Land Use Allocation – The Model begins with a base-year land use and distributes county- wide estimates of housing and employment growth to TAZs based in part on accessibility and the availability of land for development (based on zoning, physical constraints, and existing land use). As indicated in Figure 3, the model includes a land use-transportation feedback loop that accounts for the (1) the effect of new housing and jobs on the transportation system and (2) the effect of transportation on where housing and jobs are located.
Figure 3: Model Process
Trip Distribution Mode Assignment Generation Choice
Land Use Allocation
LAND USE ASSUMPTIONS As noted above, the Model distributes region-wide estimates of household and employment growth to TAZs which represent specific areas of the County. Expected growth used in the model, for 5 year increments by TAZ and total, have recently been revised by the Chittenden County Regional Planning Commission (CCRPC) and CCMPO for the
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2030 Metropolitan Transportation Plan (MTP). These new figures were used in the model runs for this study1. The regional growth totals establish the upper limit of new households and employment within the County. The Model can be used to distribute some or all of the growth across the County based on zoning, accessibility, existing land use, etc. It is also possible to manually enter households and employment from specific development projects. The consultants for the Circumferential Highway Environmental Impact Study (EIS) developed a list of anticipated development projects in several towns in and around the study area2. As part of this project the list was reviewed, as well as similar lists from the recently completed US 2 Corridor Study and the Dorset St Corridor Study. With the assistance of the Town and City Planners the list was then refined with the most recent information concerning future development assumptions in the City of South Burlington and the Town of Williston. The Burlington International Airport was also consulted to confirm their growth and development plans. These refined assumptions were used to create a revised “permitted land use” input file that includes future increases in households and employment anticipated in each TAZ in the project area. A complete list of these permitted land uses has been included in Appendix B.
HIGHWAY NETWORK ASSUMPTIONS Separate model networks were developed for each analysis year and set of sub-alternatives. The future analysis year coincides with the latest update to the Chittenden County Metropolitan Transportation Plan (MTP) - 2030. Highway improvement projects which are planned in the county were included in the future scenarios for this project, and were derived from the 2025 MTP with the assistance of the CCMPO. An interim analysis year (2018) was also derived and analyzed which looked at only a subset of the full 2030 network improvements. A full list of network improvements is included in Appendix C.
CIRCUMFERENTIAL HIGHWAY VTrans is currently conducting an Environmental Impact Statement for segments A-B of the Circumferential Highway (the “Circ” – See Figure 4) from I-89 just east of Exit 12 to the VT 117/VT 289 interchange. The EIS is ongoing (a Draft EIS was released in August of 2007) and the most recent updates are available at http://www.circeis.org/. A preferred alternative has not been selected as of July 2009. The future year (2030) was studied under three possible Circ scenarios: 1) No further Circ improvements, 2) With additional Circ segments A+B, and
1 See Household Employment Forecast Endorsement Memo from the RPC, 1/22/07
2 Received from CCMPO, 1/26/07.
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3) With all future proposed Circ segments (A-J).
Figure 4: Circ Highway Segment Map
TRAFFIC SCENARIOS The following scenarios were evaluated as part of this study: 2018 Base: No new interchange, but with the planned network improvements and additional land use assumed for 2018 (see Appendix B). 2018 Diamond Interchange: The base condition with a new I-89 Interchange with all ramps directly intersecting Hinesburg Road in a traditional diamond layout. 2018 Modified Diamond Interchange: The base condition with a new I-89 Interchange. Both southbound ramps and the northbound on-ramp would be configured in a traditional diamond layout. The northbound off-ramp would intersect Tilley Drive approximately 1,000 feet east of Hinesburg Road. 2030 Base: Existing conditions with the planned network improvements and additional capacity assumed to be constructed by 2030 (see list of improvements in Appendix C). These improvements are consistent with the 2025 Chittenden County Metropolitan Transportation Plan (MTP). 2030 Diamond Interchange: The base condition with a new I-89 Interchange with northbound and southbound ramps configured in a traditional diamond layout. No additional Circumferential Highway segments are included in this scenario.
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2030 Modified Diamond Interchange: The base condition with a new I-89 Interchange. Both southbound ramps and the northbound on-ramp would be configured in a traditional diamond layout. The northbound off-ramp would intersect Tilley Drive approximately 1,000 feet east of Hinesburg Road. No additional Circumferential Highway segments are included in this scenario. 2030 Modified Diamond Interchange with Circ AB: The base condition with a new I- 89 Interchange using the modified diamond geometry. The sections A+B of the Circumferential Highway are also included in this scenario. 2030 Modified Diamond Interchange with Full Circ: The base condition with a new I-89 Interchange using the modified diamond geometry. The completed Circumferential Highway is included in this scenario.
PIVOTING The traffic turning movement volumes used in the future analyses in this report were derived using a combination of the county model output and existing known traffic volumes through a technique referred to as “pivoting”. The pivoting process is based on the concept that an existing ground count is the best starting point for estimating scenario traffic volumes at an intersection. It uses the change in volumes estimated by the model to adjust the ground counts. Thus results from a model run which represents current conditions is subtracted from results for future scenarios, and then the actual ground counts are added back in. Where new intersections, or approaches to intersections are being created only the traffic volumes estimated by the model are considered (with slight adjustments to represent the Design Hour). This is because there are no existing ground counts to pivot off from. A more detailed explanation of this process is included in the Appendix D.
OTHER DEVELOPMENT VOLUMES
Park & Ride The CCMPO has developed a regional park and ride prioritization plan that designates the Exit 12B as a potential location for a future park and ride lot. RSG has developed a preliminary estimate of trip generation and distribution of the park and ride included in the traffic analysis. Since intercepting trips from the east and south would be one of the primary purposes of this park and ride, it was assumed the facility would be located just south of the interchange. The analysis assumed the park and ride lot would have 150 parking spaces in 2018 and 200 spaces in 2030. The effect of the additional traffic in the study area is included in the analysis.
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Pizzagalli Properties - “Tilley Subdivision” Due to the close proximity and imminent nature of this development, which is currently well under construction, the actual trip generation analysis from the traffic impact study1 was substituted for the traffic estimated by the regional model for this TAZ.
VOLUME ADJUSTMENT FACTORS This section describes the methodology used to obtain design hour adjustments and assess the delay and level of congestion at the study intersections.
Development of 2005 PM Peak Hour Design Hour Traffic Volumes Turning movement traffic counts at the study intersections were obtained from the CCMPO, VTrans, and RSG data archives. The ground counts have been adjusted in two ways. First, the ground counts were adjusted to reflect the design hour of traffic. The design hour is the 30th highest hour of traffic for the year, the design standard in Vermont. The design hour adjustments use the AADT data from Automatic Traffic Recorders (ATRs) that VTrans use in their annual traffic analyses. Their data gives an AADT estimate for study roadway segments and using the “K” factor2 for urban highways (10.4%) a design hourly volume (DHV) is derived for each study intersection. The second adjustment accounts for annual growth in background regional traffic. The annual urban growth adjustment of 0.47% per year was assumed for all study intersections; taken from the latest VTrans Red Book3 growth rate for urban highways. The majority of the traffic counts obtained were either counted in 2004 or 2005 therefore requiring little annual adjustment.
FUTURE SCENARIO TRAFFIC VOLUMES Results from the traffic model runs were first analyzed for order of magnitude changes to see what patterns or trends may be recognized. Figure 5 show the total traffic volume at each study intersection for each future scenario, and in the existing condition, where appropriate. Findings include: Traffic in the project area will increase substantially by 2018 with or without the proposed interchange. This is due, at least in part, to the Tilley Drive connection to Community Drive, which is assumed in the base case as well as the build alternatives, and allows another
1 D.L. Hamlin Consulting Engineers, 3/24/08
2 The ratio of design hour volume / AADT
3 Continuous Traffic Counter Grouping Study and Regression Analysis, VTrans, 2006
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access route to and from the busy Williston Growth Center. The development in South Burlington’s City Center and Southeast Quadrant also play a significant role in the expected growth. Overall intersection volumes would be reduced due to the construction of either interchange alternative. This is likely due to traffic being diverted to the interstate, which more efficiently gets them to their intended destination. Future traffic volumes are reduced in the project area by either Circ alternative studied (Circ A+B, or Full Circ). With the Tilley Drive connector, future traffic is expected to dominate the eastern entrance to Technology Park – suggesting that the western entrance should ultimately tee into the Tilley Drive / Community Drive roadway, as sketched below:
STOP Tilley Dr. Community Dr.
Suggested alignment
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SCENARIO VOLUME GRAPHICS Figure 5: Traffic Scenario Volumes at the Study Intersections
Traffic in the project area is Analysis Intersection Traffic Volumes 4000 expected to increase for all The no-build base case is future scenarios - with or 3500 consistently higher than the without the interchange build conditions 3000
2500
2000
1500
1000
Overall vehicles/hr in Intersection in vehicles/hr Overall 500
0 VT 116 - SB VT 116 - NB VT 116 - Tilley Kennedy Drive - Kimball Avenue - Kimball Avenue - Kimball Avenue - Tilley Drive - NB Ramps Ramps Drive Hinesburg Road Kennedy Drive Community Community Off-Ramp Intersection Drive West Drive East Raw Count Data Balanced DHV Adjusted Raw Counts 2018 Base 2018 Diamond 2018 Diamond with Tilley 2030 No Build Base 2030 Diamond 2030 Diamond with Tilley Connection 2030 Diamond with Tilley Connection and Circ AB 2030 Diamond with Tilley Connection and Full Circ
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An additional model run was made that included the connector road from Tilley Drive through the O’Brien parcel to Kimball Avenue. The resulting overall change in traffic expected due to this connector is about 260 more cars entering / exiting the intersection (see Figure 6 below), assuming the northbound off ramp ties into Tilley Drive, as shown.
Figure 6: Expected Change in Traffic Due to Tilley / Kimball Connector through O'Brien Property (2018) O’Brien Property Connector
140 280
+140 -70
-20 +60 +10
Traffic volume turning movement diagrams are presented in Appendix E for the various alternatives, which are described in the following sections. The effects of the O’Brien Connector were not included in these volumes, or subsequent analyses.
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EVALUATION METHODOLOGY The following methodology was used to evaluate geometric alignment options for the Exit 12B interchange traffic scenarios: 1) Design intersections to accommodate the scenario volumes in keeping with the VTrans’ LOS Policy. Assess need for turn lanes and overall node capacity. Develop appropriate alternatives. 2) Develop signal timing and phasing (where appropriate) to maximize coordination and flow through the area. 3) Assess queuing and delay to refine design. 4) Adjust geometries (number of lanes lane and lane use) as necessary. 5) Re-evaluate LOS and queuing to assess any changes resulting from design adjustments.
LOS Methodology Level-of-Service (LOS) is a qualitative measure describing the operating conditions as perceived by motorists driving in a traffic stream. The 2000 Highway Capacity Manual (HCM) defines six grades to describe the level of service at an intersection. LOS is based on the average delay per vehicle. Table 1 shows the various grades, qualitative descriptions, and quantitative definitions for unsignalized and signalized intersections.
Table 1: LOS Criteria for Intersections
LOS CHARACTERSTICS SIGNALIZED DELAY UNSIGNALIZED DELAY (sec) (sec) A Little or no delay < 10.0 < 10.0 B Short delays 10.1-20.0 10.1-15.0 C Average delays 20.1-35.0 15.1-25.0 D Long delays 35.1-55.0 25.1-35.0 E Very long delays 55.1-80.0 35.1-50.0 F Extreme delays 80.0< 50.1< The VTrans policy on LOS1 states that: “It is the Agency’s policy to design its highways and to require others accessing its facilities to effect improvements that will maintain a LOS “C” for the prescribed design period. In interpreting this policy, LOS refers to the overall LOS for the particular facility as defined in the latest HCM.”
1 Vermont Agency of Transportation (VTrans) Highway Design “Level of Service” Policy, 31 May 2007.
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The level of service policy provides further guidance for minor stop controlled intersections: “For two-way stop controlled intersections, the HCM does not define a procedure for obtaining an overall LOS or a LOS for major street approaches. Therefore, VTrans LOS Policy for two-way stop controlled intersections is to maintain a LOS “D,” or better, for side roads with volumes exceeding 100 vehicles/hour for a single lane approach, or 150 vehicles/hour for a two lane approach. No LOS criteria are in effect for volumes less than these. “VTrans' main objective at unsignalized two-way stop controlled intersections is to minimize potential consequences when vehicle operators exit stop-controlled side streets by accepting unsafe gaps in the major street through traffic.” In addition to LOS and delay, VTrans has recommended using Volume to Capacity (V/C) ratios when analyzing capacity at stop-controlled intersections. A V/C ratio less than 1.0 indicates that adequate capacity is available on a specific approach, even if the LOS is F. Synchro (v7), a traffic analysis software package from Trafficware, was used to conduct the congestion and queuing analysis of the study intersections. The Synchro output which is consistent with the 2000 Highway Capacity Manual methodology was used for this report. SimTraffic was also used, in combination with Synchro, to provide a comprehensive picture of vehicle operations at the Exit 12B interchange. The level of service summary tables display the HCM results from Synchro. The SimTraffic data was used to display estimated vehicle queues at the study intersections. Because SimTraffic is a stochastic model, using discrete vehicles, it can account for queue interactions between signals resulting in more accurate estimates of queue lengths and vehicle operations. For the roundabout alternative aaSidra (Akcelik & Associates, v3.2) was employed using the latest HCM unsignalized methodology for determining LOS.
ALTERNATIVES The alternatives studied are: 1. Simple diamond interchange with traffic signals 2. Simple diamond interchange with roundabouts 3. Modified diamond with traffic signals 4. Modified diamond with roundabouts 5. Standard SPUI 6. Modified SPUI
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Diagrammatic sketches of each alternative ramp configuration studied are presented in Figures 7-12 below.
Figure 7: Simple Diamond with Traffic Signals
N Tilley Dr
I-89
VT116
Figure 8: Simple Diamond with Roundabouts
N Tilley Dr
I-89
VT116 Figure 9: Modified Diamond with Traffic Signals
N
Tilley Dr
I-89
VT116
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Figure 10: Modified Diamond with Roundabouts
N
Tilley Dr
I-89
VT116
Figure 11: Single Point Urban Interchange
N
Tilley Dr
I-89
VT116
Figure 12: Modified Single Point Urban Interchange
N Tilley Dr
I-89
VT116
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TRAFFIC ANALYSIS & LANE REQUIREMENTS Traffic volumes were developed and a congestion analysis was performed for the design year 2018, which was found to be the worst case compared to the 2030 scenario. The County Transportation Model results from the previous project phase were further refined to represent the two SPUI Alternatives. Traffic volumes for each alternative have been updated to include the latest trip generation information from the Pizzagalli Properties development, which is currently under construction for Phase II and in permitting for Phase III.1 Turning movement volume maps for each of these alternatives have been provided in Appendix E. Note that model results for the 2030 time period resulted in lower volumes due to improvements anticipated by the Metropolitan Transportation Plan, and therefore was not analyzed.
SIMPLE DIAMOND INTERCHANGE WITH TRAFFIC SIGNALS Using the steps noted above the Simple Diamond Interchange option was evaluated for the 2018 planning horizon. The optimal signalized geometry is shown in Figure 13. This includes a 5-lane bridge, with two-travel lanes in each direction with a center storage pocket lane. Two through lanes are expected on Hinesburg Road north and south of the interchange. All signalized alternatives assume signal coordination. While this geometry provides adequate Levels of Service, expected southbound queuing at the middle traffic signal (the northbound on- and off-ramps) exceeds available space between intersections (see Congestion Analysis on page 26). Since traffic at this intersection is expected to increase beyond the 2018 time horizon, no further analysis was performed, assuming this queuing issue is a fatal flaw for this alternative.
1 Reference “Tilley III Subdivision” traffic analysis by DL Hamlin Engineers, date 3-24-08
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Figure 13: Intersection Geometry - Traffic Signals and Simple Diamond Interchange (2018 PM Scenario)
Tilley Dr.
~600 feet
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Table 2: Simple Diamond Interchange with Traffic Signals - 2018 PM Scenario 2018 PM Diamond Interchange SimTraffic Delay Link Length LOS V/C Ratio Maximum (Sec/veh) (feet) Queue (ft) VT 116 - Tilley Drive Overall B 18.6 -- Westbound Left (Tilley Drive) C 31.6 0.73 450 150 Westbound Right (Tilley Drive) C 24.3 0.16 300 >2000 Northbound Thru (VT 116) B 17.0 0.55 123 177 Northbound Right (VT 116) B 12.0 0.14 103 177 Southbound Left (VT 116) B 12.2 0.25 199 >2000 Southbound Thru (VT 116) A 7.5 0.26 1565 >2000 VT 116 - NB Ramps Overall C 24.2 -- Westbound Left (NB Off-Ramp) C34.00.49112- Westbound Right (NB Off-Ramp) C31.30.17314- Northbound Left (VT 116) D 35.5 0.76 245 369 Signalized Northbound Thru-Right (VT 116) A 5.0 0.34 409 369 Southbound Thru-Right (VT 116) C 23.0 0.76 150 96 VT 116 - SB Ramps Overall C 26.4 -- Eastbound Left (SB Off-Ramp) C30.10.29147- Eastbound Thru-Right (SB Off-Ramp) D40.90.70151- Eastbound Right (SB Off-Ramp) D40.90.70156- Northbound Thru-Right (VT 116) C 24.6 0.79 642 >2000 Southbound Left (VT 116) D 40.3 0.86 352 369 Southbound Thru (VT 116) A 8.9 0.61 468 369 To illustrate the deficiency discovered in this analysis a computer “screenshot” of a typical simulation is presented in Figure 14.
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Figure 14: Simulation Example of Excessive Queuing Southbound and Westbound at Tilley Drive (2018 Signalized Simple Diamond)
VT 116
Long Queues on Southbound and Westbound Approaches
Tilley Drive
SIMPLE DIAMOND INTERCHANGE WITH ROUNDABOUTS The simple diamond configuration with roundabouts would result in three roundabouts in a configuration similar to the one shown in Figure 15, but tighter confines (for comparison see spacing noted in Figure 13). This example is from the state of Michigan where roundabouts are very common and well known to drivers. While this solution may yet prove feasible for the Exit 12B site, these difficult geometric constraints and the fact that few roundabouts currently exist in Vermont lead us to conclude that other, more conventional options should be explored first.
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Figure 15: Example of 3 roundabouts at an interchange in Brighton, Michigan (photo credit DLZ Michigan Inc.)
~1,075 feet
MODIFIED DIAMOND INTERCHANGE WITH TRAFFIC SIGNALS The optimal signalized lane requirements for the Modified Diamond Interchange are shown in Figure 16. This concept includes a 5-lane bridge, with a single thru lane in each direction and double left-turn lanes for the entrance ramps. A seven foot barrier median is also included in the design between the signalized intersections. The northbound on-ramp is aligned to intersect with Tilley Drive and the northbound off-ramp terminates further east on Tilley Drive (inset to Figure 16). This geometry accommodates the expected traffic demands with overall LOS C and minimal queuing impacts. Specific movements may operate at a LOS that is lower than C with long queues; however, the queues are within the overall link length. The detailed results from the operational analysis are shown in Table 3. The configuration at the northbound off-ramp at Tilley Drive would be signalized with one lane on each approach. Critical Features: - Sufficient spacing between signals provides capacity for queues on VT 116
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- Long queues exist on interstate ramps and Tilley Drive
Figure 16: Modified Diamond Interchange - Traffic Signals
NB On-Ramp
NB Off-Ramp
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Table 3: Modified Diamond - 2018 Capacity Analysis
2018 PM Peak Hour Modified Diamond Avg. SimTraffic SimTraffic Link V/C LOS Delay Average Maximum Length Ratio (s/veh) Queue (ft) Queue (ft) (feet) Tilley Drive - NB Off-Ramp Overall C 23.0 -- -- Eastbound (Tilley Drive) A 9.6 0.50 175 623 1000 Westbound (Tilley Drive) C 28.9 0.92 389 864 >1000 Northbound Left (NB Off-Ramp) C 27.8 0.72 152 310 325 Northbound Right (NB Off-Ramp) B 15.4 0.04 40 162 >1000 VT 116 - Tilley Drive - NB On-Ramp Overall C 23.0 -- -- Westbound Left (Tilley Drive) C 29.3 0.81 237 349 450 Westbound Thru (Tilley Drive) B 19.0 0.13 79 468 1000 Westbound Right (Tilley Drive) C 21.0 0.37 126 240 300 Northbound Left 1 (VT 116) B 19.8 0.78 93 215 250 Northbound Left 2 (VT 116) B 19.8 0.78 109 301 450 Northbound Thru (VT 116) B 10.3 0.41 78 343 450
Signalized Northbound Right (VT 116) A 5.2 0.17 52 170 300 Southbound Left (VT 116) C 26.1 0.45 95 225 300 Southbound Thru (VT 116) C 31.4 0.66 155 304 >1000 VT 116 - SB Ramps Overall C 27.8 -- -- Eastbound Left (SB Ramp) C 29.3 0.31 145 300 600 Eastbound Thru-Right (SB Off-Ramp) D 51.9 0.82 605 862 1000 Eastbound Right (SB Off-Ramp) D 51.9 0.82 275 450 600 Northbound Thru-Right (VT 116) C 24.6 0.80 292 436 >1000 *Southbound Left 1 (VT 116) D 42.6 0.82 134 233 200 Southbound Left 2 (VT 116) D 42.6 0.82 154 303 450 Southbound Thru (VT 116) A 3.7 0.70 74 305 450 *queues exceed capacity, however spillover into Southbound Left 2 does not effect operation.
MODIFIED DIAMOND INTERCHANGE WITH ROUNDABOUTS Two-lane urban roundabouts were evaluated in asSidra1 at the two ramp junctions with Hinesburg Road. General schematics of the roundabout layout are shown in Figure 17. The necessary roundabout at Tilley Drive and the northbound off-ramp would be a hybrid one lane roundabout with single lane approaches but a 2-lane exit on the west approach would allow the eastbound lane to act as a slip lane – see Figure 18. These schematics are not meant to represent actual striping or design layout. Rather, they display potential approach lane layout for capacity assessment purposes.
1 Akcelik & Associates, V3.2
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The 2018 roundabout analysis required additional capacity for the southbound right turn onto Hinesburg Road southbound. Slip lanes were added to the roundabouts to provide the additional capacity.
Figure 17: Intersection Geometry – Modified Diamond Interchange – Roundabouts on VT116
Northbound On-Ramp / Tilley Intersection Southbound Ramps Intersection
Figure 18: Intersection Geometry – Modified Diamond Interchange – Roundabout on Tilley Drive
Northbound off-ramp at Tilley Drive
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Table 4 shows the expected level of service, corresponding delay, V/C ratios, and maximum queue lengths for the Modified Diamond with roundabouts used as intersection control. Even with slip ramps for right turns on several approaches, the analysis results show poor performance at the Tilley Drive and the southbound approaches to the northbound ramp intersection.
Table 4: Roundabouts with Modified Diamond Interchange – 2018 PM Peak Hour
VT 116 SB Off-Ramp Overall NB SB EB 95th % 95th % 95th % Queue Queue Queue Location / Intersection Delay LOS Delay LOS V/C (ft) Delay LOS V/C (ft) Delay LOS V/C (ft) 2018 9.6 LOS A 13.7 LOS B 0.734 249 7.1 LOS A 0.505 0 7.4 LOS A 0.467 26 VT 116 -SB Ramps 2030 9.4 LOS A 13.4 LOS B 0.727 243 7.1 LOS A 0.486 0 7.1 LOS A 0.501 23
VT 116 Tilley Drive Overall NB SB WB 95th % 95th % 95th % Queue Queue Queue Location / Intersection Delay LOS Delay LOS V/C (ft) Delay LOS V/C (ft) Delay LOS V/C (ft) VT 116 - Tilley Drive - 2018 37.0 LOS E 10.0 LOS B 0.479 112 100.6 LOS F 0.980 709 25.0 LOS C 0.910 530 NB On-Ramp 2030 35.3 LOS E 10.2 LOS B 0.504 121 97.2 LOS F 0.976 694 21.5 LOS C 0.873 432
Tilley Drive NB Off-Ramp Overall EB WB Northbound 95th % 95th % 95th % Queue Queue Queue Location / Intersection Delay LOS Delay LOS V/C (ft) Delay LOS V/C (ft) Delay LOS V/C (ft) Tilley Drive - NB Off- 2018 8.9 LOS A 2.5 LOS A 0.232 - 8.5 LOS B 0.758 345 14.9 LOS B 0.565 143 Ramp 2030 10.8 LOS B 5.4 LOS A 0.204 - 10.1 LOS B 0.702 281 16.0 LOS B 0.561 140
STANDARD SINGLE POINT URBAN INTERCHANGE The optimal signalized lane requirements for a Single Point Urban Interchange (SPUI) are shown in Figure 19. This includes a 6-lane bridge, two-travel lanes in each direction, two-turning lanes for each of the interstate on-ramps, and a single traffic signal operating both ramps. This geometry accommodates the expected traffic demands with a reported overall LOS C, but with some queuing impacts. The northbound and southbound movements on VT 116 continue to interact with the SPUI and the Tilley signals. The closely spaced signals will experience queue interaction. This option does not have spare capacity to shift to the VT 116 mainline, limiting opportunities to improve the deficiency. The detailed results of the operational analysis are shown in Table 5.
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Critical Features: - Queues between the SPUI signal and the VT 116-Tilley Drive signal continue to interact. - SPUI provides better operations for ramps with minimal queuing and good V/C ratios.
Figure 19: Single Point Urban Interchange - Traffic Signals
Northbound on-ramp
Northbound off-ramp
New bridge
Southbound off-ramp
Southbound on-ramp
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Table 5: Standard SPUI Capacity Analysis - 2018 PM Peak Hour 2018 PM Peak Hour: 6-lane Bridge SPUI SimTraffic SimTraffic HCM Delay Link Length LOS V/C Ratio Average Maximum (sec/veh) (feet) Queue (ft) Queue (ft) VT 116 - Tilley Drive Overall C 23.6 -- - - Westbound Left (Tilley Drive) C 31.1 0.79 1013 1096 >1000 Westbound Right (Tilley Drive) C 22.1 0.24 794 1069 350 Northbound Thru (VT 116) C 25.1 0.73 140 282 300 Northbound Right (VT 116) B 10.1 0.18 63 217 300 Southbound Left (VT 116) D 46.9 0.68 130 256 300 Southbound Thru/Right (VT 116) B 11.8 0.29 122 273 >1000 SPUI Signal Overall C 30.0 -- - - Eastbound Left (SB Off-Ramp) C 33.5 0.30 59 151 270 Signalized Eastbound Right (SB Off-Ramp) D 38.3 0.60 67 298 270 Westbound Left (NB Off-Ramp) D 47.0 0.76 127 159 375 Westbound Right (NB Off-Ramp) B 10.0 0.27 128 165 375 Northbound Left (VT 116) D 36.8 0.73 124 234 450 Northbound Thru (VT 116) C 21.2 0.31 104 229 450 Northbound Right (VT 116) C 20.0 0.16 - - 450 Southbound Left (VT 116) C 30.2 0.77 126 200 270 Southbound Thru (VT 116) B 19.4 0.64 194 300 290
MODIFIED SINGLE POINT URBAN INTERCHANGE The standard SPUI was modified by shifting the northbound on-ramp to align with Tilley Drive. The ramp alignment improves efficiency for the entire system by consolidating intersections and movements. The modified SPUI maintains the 6-lane cross section along VT 116 and shifts the northbound on-ramp to align with Tilley Drive. This geometry accommodates the expected traffic demands with overall LOS C and minimal queuing impacts. Specific movements may operate at LOS lower than C with long queues; however, they can be accommodated with additional design changes or within the overall link length. The operational analysis is shown in Table 6. The distance between the SPUI signal and the Tilley Drive signal still presents some queuing challenges, which shows the maximum queues interacting with each other. Available capacity at the Tilley Drive signal could reduce the potential for interaction. The queues are not to the degree that they cannot be overcome. Critical Features: - Queues between the SPUI signal and the VT 116-Tilley Drive signal continue to interact but better operations at VT 116-Tilley Drive allow for potential improvements. - SPUI provides better operations for ramps with minimal queuing and good V/C ratios.
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Figure 20: Modified Single Point Urban Interchange - Traffic Signals
Northbound on-ramp
Northbound off-ramp New bridge
Southbound off-ramp
Southbound on-ramp
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Table 6: Modified SPUI Capacity Analysis - 2018 PM Peak Hour
2018 PM Peak Hour: Modified SPUI (6-lane Bridge ) SimTraffic SimTraffic HCM Delay Link Length LOS V/C Ratio Average Maximum (sec/veh) (feet) Queue (ft) Queue (ft) VT 116 - Tilley Drive Overall C 25.9 ---- Westbound Left (Tilley Drive) D 40.2 0.83 234 395 450 Westbound Thru (Tilley Drive) D 41.4 0.84 234 380 >1000 Westbound Right (Tilley Drive) C 23.0 0.23 113 264 350 Northbound Thru (VT 116) C 22.5 0.69 180 281 300 Northbound Right (VT 116) A 6.9 0.18 80 219 300 Southbound Left (VT 116) D 49.3 0.71 94 198 300 Southbound Thru (VT 116) B 10.4 0.2 64 140 >1000 Southbound Right (VT 116) A 9.9 0.1 26 74 300 SPUI Signal Overall C 30.9 ---- Signalized Eastbound Left (SB Off-Ramp) C 33.4 0.30 59 134 270 Eastbound Right (SB Off-Ramp) D 52.5 0.92 24 283 270 Westbound Left (NB Off-Ramp) D 46.5 0.75 144 309 375 Westbound Right (NB Off-Ramp) A 0.2 0.17 - - 375 Northbound Left (VT 116) C 28.6 0.56 115 202 450 Northbound Thru (VT 116) C 21.9 0.32 108 197 450 Northbound Right (VT 116) C 20.6 0.16 1 35 450 Southbound Left (VT 116) C 27.5 0.73 89 177 270 Southbound Thru (VT 116) C 28.1 0.80 193 287 290
GEOMETRIC OPTIONS SUMMARY Several of the studied alternatives were shown to be operationally lacking, including; 1) The simple diamond interchange (with traffic signals) – the close proximity of the northbound ramps and Tilley Drive, which is expected to serves heavy traffic in the future with the planned connection to Technology Park in Williston creates problematic traffic signal phasing requirements. In particular, the westbound traffic competes with the similarly large volume southbound on VT116 resulting in unacceptable queuing and delay. 2) Roundabout alternatives: a. The simple diamond with roundabouts was not studied due to the difficult geometric constraints and likely driver confusion created by such closely spaced intersections. b. The modified diamond with roundabouts resulted in the need for more than two circulating lanes in the northern roundabout on VT 116 at Tilley Drive. This is due in part to the high volume of traffic expected on the Tilley Drive approach. These circulating lanes would be in addition to slip lanes for certain heavy right turns. While a three lane roundabout is not unprecedented, it presents a decidedly large leap in innovation to traffic control in Chittenden County since no modern roundabouts have been built on any state controlled facilities to date.
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3) The standard SPUI – again, queue interaction between closely spaced intersections creates problematic signal timing and phasing requirements. Two interchange alignment options were shown to operate acceptably, and were continued to the conceptual design phase: - Modified Diamond Interchange - Modified SPUI Interchange
CONCEPTUAL DESIGN SKETCHES The two modified interchange designs, the diamond and SPUI, have been carried forward from the traffic operational analysis and specific geometric designs have been developed. Preliminary concept sketches for the Modified Diamond are shown in Figure 21 and Figure 22. The Modified SPUI is shown in Figure 23. Larger scale versions of these drawings are presented in Appendix F. Specific criteria for the critical elements of these designs is summarized in Appendix F.
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Figure 21: Modified Diamond Interchange – Concept Sketch (Northern Half)
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Figure 22: Modified Diamond Interchange – Concept Sketch (Southern Half)
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Figure 23: Modified SPUI Interchange – Concept Sketch (Northern Half)
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Figure 24: Modified SPUI Interchange – Concept Sketch (Southern Half)
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COST ESTIMATES Itemized cost estimates were prepared for the two interchange options and are provided in Appendix G. The resulting estimated construction costs of the interchange options, in 2008 dollars are as follows: - Modified Diamond Interchange: $29.3 Million - Modified SPUI Interchange: $43.5 Million These estimates take into account all relevant construction and engineering costs save for Right-of- Way or cost escalation due to inflation. It should also be noted that these cost estimates do not include costs for additional work on the interstate such as widening to three lanes in each direction, or the cost of the necessary Environmental Impact Statement. Material costs were derived from a combination of the latest bid summaries by VTrans, as well as a recent interchange reconstruction in Derry, NH on I-93. A full summary of the assumptions and cost estimate methodology is also included in Appendix G.
SUMMARY OF FINDINGS The existing Hinesburg Road / I-89 overpass bridge is in good condition, but it is narrow for current requirements and expectations which include the desire for on-road bicycle use. The review of environmental and cultural resources shows a number of wetlands and archeologically sensitive areas within the path of the studied improvements. The most notably of these potential impacts is the class II wetlands and archaeological site located on the eastern side of the Pizzagalli subdivision property, where the Tilley Drive extension to Community Drive is planned. The Simple Diamond Interchange, standard SPUI design, and roundabout at the VT 116- Tiley Drive intersection appear to be infeasible and were discontinued from further refinement. The Modified Diamond Interchange and Modified SPUI Interchange were found to be operationally feasible, and were continued to the preliminary concept design phase. Both feasible designs require a new wider bridge accommodating 5 or 6 lanes (depending on the alternative), plus a median and bicycle and pedestrian facilities. Geometry for the southbound exit ramp requires long approaches due to rising interstate grades combined with the need to rise to the bridge height and standard limits on ramp grades (5% in this case). The southbound exit ramp begins on a right curve with dense vegetation which keeps the ramp facility out of view – clearing may be necessary upstream of the ramp.
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For the Modified Diamond Interchange Alternative: o This alternative provides the maximum distance between traffic signals, reducing the likelihood of future queue interaction between intersections. o This alternative impacts a significant amount of Class 2 wetlands due to the northbound exit ramp leading to Tilley Drive. o This alternative requires a simpler and narrower bridge. o The Tilley Drive approach requires one more lane for this alternative.
For the Modified SPUI Alternative: o This alternative provides a more compact design, resulting in higher cost - mainly due to necessary retaining walls and a much wider bridge, but fewer wetlands impacts. o The northbound entrance ramp is significantly longer, due to the need for a lane drop from the double left from VT116, and a merge with the lane leading from Tilley Drive. This will likely create some impacts outside of the identified Right-of-Way on the Allen Rd Land Co property.
COORDINATION MEETING WITH VTRANS AND THE AGENCY OF NATURAL RESOURCES On October 22nd, 2008 the CCMPO, VTrans and representatives from various sections of the Agency of Natural Resources met to review the initial findings of this report. Elements of the presentation included: The project area The draft Purpose & Need Resource mapping Traffic modeling and alternative analysis Geometric Alternatives Discussion at this meeting included the exploration of additional alternatives that might lessen impacts to wetlands or other resources such as; 1) alternatives that do not include the planned Tilley Drive connector to Technology Park, 2) possibly moving the northbound exit ramp, or “hook ramp”, of the Modified Diamond further east, 3) alternatives exploiting Exit 13 at Kennedy Drive &
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I-189 and 4) other traffic volume scenarios that include the Circumferential Highway improvements without Section A-B (i.e. consideration of the VT2A alternatives).
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APPENDIX A – PROJECT MAPS
Wi lli st on R o ad (U S 2)
K i m b D a or l l A s v e e t
S t ive edy Dr OBrien Brothers Kenn H in es e b v u i rg r D R
d y ( t VT i 11 n 6 u ) Pizzagalli - LOT 2 m
om
Pizzagalli - LOT 6&7 Pizzagalli - LOT 1 C Technology Park LOT 8A I-89 Allen Rd Land Co / Larkin Pizzagalli - LOT 3 Tilley Drive Exit 12B Pizzagalli - LOT 4 Site Pizzagalli - Lot 5
Verizon
Davis Realty
Legend town boundaries 0.20.1 0 0.2 0.4 0.6 Exit 12B Alignment Study Parcel & ROW Bounds Project Area I Miles OBrian Brothers
H i ne sb urg O'Brien Property R o Connector ad End Public d to Kimball Ave R Sidewalk
m r
a
F Pizzagalli - LOT 2 d l
O
Tilley Drive Pizzagalli - LOT 6&7 and Rec Path alternate (existing)
NB on-ramp Pizzagalli - LOT 1 Technology Park LOT 8A
Allen Rd Land Co / Larkin Pizzagalli - LOT 3
Pizzagalli Pizzagalli Com munit NB on-ramp y Drive Proposed Tilley Pizzagalli - LOT 4 Drive Extension NB off-ramp Pizzagalli - Lot 5 alternate NB off-ramp SB off-ramp
SB on-ramp
Davis Realty Verizon
Legend
Paths_SW Reserved ROW Wetlands-sketched 250125 0 250 500 Ramp Alternatives Parcel & ROW Bounds Wetlands-mapped Feet Connector Roads Floodzone New Intersection Planned Rec Paths Archaelogical-sketched I Exit 12B Alignment Study - Constraints Map
APPENDIX B – LAND USE ASSUMPTIONS
For Exit 12B - assume all specific development implemented by 2018, new development from2018-2030 will be allocated by LUAM as of 12-26-07 by MCS / RSG, Inc. TAZ S. Burlington Project Description - from Dorset St Corridor Project Housing Employment / Commercial Total Square Total More Notes - base data from Dorset St Project and / or updated late October 2007 as by '10 by '15 Total HU Breakdown / notes Feet by '10 by '15 Employment noted 93 Quarry Hill Residential 64 217 281 updated 1-10-08 by JBH; best estimate 98 City Center 139 139 277 from lateset draft EIS Med-High 338 338 675 refined information from Marty Kennedy, VHB, 10/07, assume 1/2 by '05, 1/2 by '15 99 City Center 30 30 60 from lateset draft EIS Med-High 115 115 229 refined information from Marty Kennedy, VHB, 10/07, assume 1/2 by '05, 1/2 by '15 101 City Center 145 145 290 from lateset draft EIS Med-High 387 387 774 refined information from Marty Kennedy, VHB, 10/07, assume 1/2 by '05, 1/2 by '15 103 City Center 14 14 28 from lateset draft EIS Med-High 119 119 238 refined information from Marty Kennedy, VHB, 10/07, assume 1/2 by '05, 1/2 by '15 113 O'Brien Residential Development 110 110 220 0 114 Pizzigalli Tilley Drive Office Park All office Med-Low 350,000 290 345 635 discussion with Bob Bouchard, Pizzagalli Properties, 10/07, includes 2 bldgs built, 1 near completion. Employment scaled 350/210 for add'l s.f. added. Assume 1/4 by '10 and done by '15 121 Technology Park 300 KSF office, 55 KSF light Med-Low 355,000 161 484 645 s.f. verified by Abby Lisius, Trudell CE 11/1/07, includes 1 bldg just completed (72k), 1 industrial under constr. (54.5k) assume 1/4 by 10, 3/4 by 15 125 Heatherfields 89 0 89 updated 1-10-08 byJBH 129 Hill Farm Mixed Use 170 170 600 KSF office, 25 KSF Med- 625,000 1,137 1,137 refined information from Bob White, ORW 10/07 - assume not started by '10, done by '15 retail Low/Med- High 131 Meadowlands Business Park 36 KSF office, 130 KSF Med- 166,000 147 147 - assume not started by '10, done by '15 Light Industrial Low/Low 137 Elementary School 750 Students School Not Used 150 150 Employment for the school is based on ratio of 0.2 employees per student in current South Burlington Elementary Schools 137 Rye Residential Development 75 75 Med-Low 77 77 154 138 Housing Dev off Park Road 0 eliminated 1-10-08 by JBH 140 Farrell Residential Development 48 48 updated 1-10-08 by JBH; best estimate 141 Vermont National Country Club 250 80 330 updated 11-2-07 e-mail JB Hinds 143 Gardner Residential Development 26 26 149 South Village 100 232 332 150 Cider Mill Phase I Residential 149 149 150 Cider Mill Phase II 48 130 178 updated 11-2-07 e-mail JB Hinds 150 Marceau Meadows 75 75 150 150 Williams 10 10 150 Autumn Hill Rd 15 15 150 Dorset Farms 45 45 150 Falkenburg Residential Development 14 14
150 Fresh Market at corner of Nowland, All Retail Med-High 15,000 27 27 Dorset, Old Cross Totals 2,787 1,511,000 4,811
TAZ S. Burlignton Assumptions from Office SF Retail SF Total Source the Circ Highway by '10 by '15 Total HU by '10 by '15 Employment 113 Snyder Lancaster 70 70 Completed 2006 116 LNP, Inc. 69050 Med-Low 173 173 Completed 2006 124 City's Edge 63 63 - Completed 2006 124 Eastwood Commons 90 90 - completed 2007 126 Forest Glen a.k.a. Heatherfields 0 0 - duplicate of Heatherfields 131 Avalanche Development 8900 Med-Low 22 22 City Planning Dept. 4/06 131 Gravelin 10000 Med-Low 25 25 City Planning Dept. 4/06 142 Lowes High 123,000 246 246 occupancy 1-17-2008 149 Farrell Spear Street 48 48 - updated 1-10-08 JBH 149 South Pointe 32 32 - completed 2006 151 Redstone 0 - project very much on hold.
Exit 12B Alignment Study - Appendix B - Page 1 TAZ other South Burlington Projects, Percent Enplanemnt Notes from US2 Corridor Study Growth 2000-2030 Total by '10 by '15 Employment 86 Burlington Intn'l Airport (BTV) 96% See BIA worksheet - Trip gen based on ALP projected enplanement growth 108 BTV South Development 600 600 See BIA worksheet - S Development Master Planning assumptions
TAZ Williston projects by '10 by '15 Total HU Hotel Rooms Commercial / Employment Notes / descriptions Total All projects updated 10-26-07 w/ data provided by Lee Nellis / Town Planner (sq feet) by '10 by '15 Employment 203, 205, Single Family 30 over the 10 year analysis period - spread out over the south end of Town 206, 207, 208, 209, 211 15 15 200 General Office/Retail Med-Low 10,000 13 13 25 retail/office (infill within the Village Center) 200 Single Family 5 5 - Village Center infill 200 Multifamily 5 5 - Lyon Property - 8 acres for income sensitive housing units, rev. 11/1/07 170 Single Family 4 3 7 - Clark subdivision 170 condos/Townhouses 30 30 - residential (Fontaine property) 174 Single Family 4 4 - residential (mountain view road to replace mini-golf) 194 condos/Townhouses 30 30 - 20 acres based on zoning densities. Judge Bryan Land 194 Single Family 7 7 - Senacal 210 Single Family 7 7 - site 7 on the map 166 Convenience Store High 12,000 40 40 Commerical (gas station, convience store on VT2A) 181 Industrial/Commercial Low 15,000 25 25 commercial - industrial. Flexible building (Munson) 183 Industrial/Commercial Low 100,000 167 167 Industrial (Robearge) 191 Industrial/Commercial Low 40,000 67 67 Commerical/Industrial (site 6 on map) 195 Industrial/Commercial Low 40,000 67 67 Industrial (site 5 on map) 178 Other, Church 10 Low Church with other amenities including soccer fields, indoor + outdoor, community meeting 10 157,000 39 39 rooms and recreation facilities. 180 condos/Townhouses 356 356 - residential/ Finney Crossing 180 Specialty Retail Med-High 25,000 50 50 retail/ Finney Crossing 180 General Office Med-Low 25,000 83 83 non-retail commercial/ Finney Crossing 186 General Office Med-Low 50,000 167 167 office/ Blair Park 188 Drug Store Med-High 30,000 60 60 retail/ Judge (North)/ drug store 188 condos/Townhouses 60 50 110 - Village Associates 193 Drug Store Med-High 10,000 20 20 retail/ Jeff Davis Expansion, north side/ Drug Store 193 Restaurant High 7,000 23 23 restaurant. High-turnover sit down. Texas Roadhouse 197 General Office Med-Low 10,000 33 33 office/ MTP 197 Specialty Retail Med-High 10,000 20 20 retail/MTP 197 condos/Townhouses 123 123 - residential/ Senacal development 197 General Office Med-Low 81,000 270 270 Office/ Senacal 197 condos/Townhouses 50 50 - Lapierre/ 78 acres of land, very wet. Maybe 30 acres to develop 198 Restaurant Med-High 5,000 17 17 restaurant/ Jeff Davis 199 condos/Townhouses 50 50 - residential/ Davis transfer of commercial to residential 199 Retail/ Commercial store Med-High 130,000 433 433 Retail - stand alone store 202 General Office Med-Low 40,000 133 133 General Office/ Jeff Davis 202 Specialty Retail Med-High 20,000 40 40 retail/ Jeff Davis Expansion 203 Hotel 50 Hotel - Motel/hotel (Ramsey parcel) 203 Gas Station High 2,000 7 7 convience store with gas station (Ramsey Land) 203 General Office Med-Low 40,000 133 133 single use office complex (Saloman site - similar uses as to Hurricane Lane) 205 General Office Med-Low 70,000 233 233 single use office complex (Qimonda R&D facility) 202 condos/Townhouses 100 100 - Davis residential 202 Hotel 200 Hotel 200 200 Hotel TOTALS 924 250 929,000 Exit 12B Alignment Study - Appendix B - Page 2 CCRPC 2006 Chittenden County Growth Forecasts 2000 2005 2010 2015 2020 2025 2030 Households 60331 59,580 63,210 66,800 71,200 77,000 83,000
2000-2005 2005-2010 2010-2015 2015-2020 2020-2025 2025-2030 Total Increment 2000-2030 Household Growth - Time Step Increments 3,407 3,630 3,590 4,400 5,800 6,000 26,827
Employment Total Employment 93,217 97,411 103,171 108,912 115,437 122,335 129,628 Retail Employment 45,038 47,064 49,847 52,621 55,773 59,107 62,630 Non-Retail Employment 48,179 50,347 53,324 56,291 59,663 63,229 66,998 Employment Growth - Time Step Increments 2000-2005 2005-2010 2010-2015 2015-2020 2020-2025 2025-2030 Total Increment 2000-2030 Total Employment 4,194 5,760 5,742 6,524 6,899 7,293 36,411 Retail Employment 2,026 2,783 2,774 3,152 3,333 3,524 17,592 Non-Retail Employment 2,168 2,977 2,968 3,372 3,565 3,769 18,819
January 2008 MPO Calculations for LUAM Core Area Growth Totals
HOUSEHOLD GROWTH ASSUMPTIONS 2000-2005 2005-2010 2010-2015 2015-2020 2020-2025 2025-2030 Total Increment 2000-2030 Increase in Total Households 3,407 3,630 3,590 4,400 5,800 6,000 26,827
CORE HOUSEHOLD GROWTH CORE HH GROWTH IN PER FILES 2,974 4,312 2,836 0 0 0 10,122 Calculated CORE HH GROWTH FOR LUAM 0 -2,037 -589 3,057 5,067 5,504 Adjusted CORE HH GROWTH FOR LUAM 0 0 0 431 5,067 5,504 11,002
NON-CORE HOUSEHOLD GROWTH NON-CORE HH GROWTH IN PER FILES 432 1,355 1,343 1,343 733 496 5,703 NON-CORE HH GROWTH FOR LUAM 000000
EMPLOYMENT GROWTH ASSUMPTIONS 2000-2005 2005-2010 2010-2015 2015-2020 2020-2025 2025-2030 Total Increment 2000-2030 Increase Total Covered Employment 4,194 5,760 5,742 6,524 6,899 7,293 36,411 Increase Retail Employment 2,026 2,783 2,774 3,152 3,333 3,524 17,592 Increase Non-Retail Employment 2,168 2,977 2,968 3,372 3,565 3,769 18,819
TOTAL EMPLOYMENT GROWTH (check sums) 4,194 6,708 7,314 4,339 6,564 7,293 36,411
CORE EMPLOYMENT GROWTH CORE EMP GROWTH IN PER FILES 2,842 5,117 5,237 0 0 0 13,196 Calculated CORE EMP GROWTH FOR LUAM 1,049 -948 -1,572 3,776 3,249 2,479 8,032 Calc CORE RETAIL EMP GROWTH FOR LUAM 913 -240 103 1,727 1,440 1,027 4,971 Calc CORE NON-RETAIL GROWTH FOR LUAM 136 -708 -1,676 2,049 1,809 1,452 3,061 Adjusted CORE EMP GROWTH FOR LUAM Adj CORE RETAIL EMP GROWTH FOR LUAM 913 0 0 1,590 1,440 1,027 Adj CORE NON-RETAIL GROWTH FOR LUAM 136 0 0 0 1,474 1,452
NON-CORE EMPLOYMENT GROWTH NON-CORE EMP GROWTH IN PER FILES 303 1,590 2,077 2,748 3,650 4,814 15,183 NON-CORE EMP GROWTH FOR LUAM 000000 0 NON-CORE RETAIL EMP GROWTH FOR LUAM 000000 0 NON-CORE NON-RETAIL GROWTH FOR LUAM 000000 0 updated jan 9, 2008
The Previous 2006 CCRPC LUAM control totals were based on the difference in the following formula [Total HHs - Non-Core PER - Core PER] between timesteps.
So for the 2005 to 2010 timestep the LUAM total was calculated as: [Total 2010 HHs - 2010 Non-Core PER - 2010 Core PER] - [Total 2005 HHs - 2005 Non-Core PER - 2005 Core PER].
The above formula means we were basically adding the 2005 non-core and core PER totals to the 2005-2010 LUAM increment. This results in a regional increase of households between 2000-2030 of approximately 99,397-60,331 = 39,066 (as compared to the RPC regional forecast increment of 26,827 households).
I believe a more appropriate way to calculate this would be [(Total 2010 HHs - Total 2005 HHs) - 2010 Non-Core PER - 2010 Core PER]. I used the revised formula to develop the "Calculated" HHs and Emp above in blue text. However, this method resulted in too much land use for the 2005- 2010 and 2010-2015 timesteps (as indicated by the negative numbers) - the regional forecast increment between these years was not enough to absorb the growth in the PER file. So, I have proposed adjusting the LUAM core area allocation to zero for those years and carrying forward the "negative balance" of households and applying that to the next timestep. In one case for non-retail employment I had to go an additional timestep to 2020-2025 before there was a positive balance of employment for LUAM to allocate in the Core areas. These adjusted figures are highlighted in yellow above. Calculating with this method does result in achieving consistency with the RPC county-wide forecast increments.
C:\Documents and Settings\Marks\Local Settings\Temporary Internet Files\OLKE3\20080109_CCMPO_12B_land_use_forecasts (3).xls
APPENDIX C – NETWORK ASSUMPTIONS
Effective ID Improvements Comments Date
Improvements included in 2015 (open for travel by 2015):
1 Blakely Rd/Lavigne Rd 2000 Add left turning lane on Blakely Rd 2 Prim Rd and Lakeshore Dr 2000 Add roundabout. 3 Heinberg/Porters Intersection 2000 Add 2 turn lanes to South approach 4 All-Way stop at Spear St./Allen Rd in South Burlington 2005 Node 580. Add SDLs for all-way stop. I-89 Exit 12 improvements in Williston: add a double left turn lane on the southbound off- ramp (also identified as a TSM project) [No other improvements at these intersections Node 532. Increase ramp node capacity to ~3,600 5 as outlined below – partial solution] 2005 vph
Dorset and Swift St node capacity correction. S Burl also has plan to Node 399. Current capacity of 2,100 should be 6 realign the Swift St turning lanes, but should not affect model capacity. 2005 increased to 3,400 to reflect existing turning lanes.
Node 624. Signalized intersection capacity should 7 Traffic signal with turning lanes at VT 15/Old Stage Rd in Essex 2005 be increased to ~3,000 to reflect turning lanes. Node 478. Current capacity should be ~3,500 - now coded at 2,700. Future 2020 Capacity should 8 US 2/7 at Blakely/Severance 2005 increase to ~4,000 Node 966. Added signalized intersection with capacity ~ 2,700. Already coded in RSG 2005 9 VT 2A Zepher Avenue Signalization 2005 base. 10 Winooski Downtown redevelopment 2005 Already coded in 2005 network. 11 Spear St./Allen Rd Traffic Signal (part of South Village improvements) 2010 Node 580 Add neighborhood network of streets in NE corner 12 Hamlet and other Developments (in the vicinity of VT 2A/US 2) 2010 of Tafts Corner Growth Center
Around Node 535 should be changed to signlized intersection with capacity ~3,400. Only affects SB off ramp and WB US 2. Signal does not control I-89 Exit 14 improvements: an additional lane on the southbound off-ramp and a signal at EB US 2. Three lanes continue from the bridge to 13 the end of the ramp where it intersects US 2 (in place as of 2007) 2010 US 2 west of the ramps. Lane should be added to reflect widening and signal node capacities should be updated when 14 Kennedy Drive widening, South Burlington (in place as of 2007) 2010 necessary (Timber, VT116, Kimball). Market St should be added along with other planned City Center road facilities. Signal on west Market St & City Center in South Burlington side exists. Need traffic control assumption for Includes Midas Dr / White St and US 2 / Mary St - Obtain configuration from Marty east end of road. Check City Center analysis for 15 Kennedy at VHB. 2010 info. 16 I89 Exit 14 - US 2 eastbound widening (Staples 3rd lane) 2015 Earmark funding available New signalized intersection just east of Maple 17 US 2 / Talcott Rd Traffic Signal 2010 Tree Pl - around node 517. Capacity ~3,000 Widening project complete between Imperial Dr and Webster Rd. Includes left turn lanes and 18 US 7/Shelburne Road widening, Shelburne/South Burlington 2010 access management Node 570. Change to signal with capacity of 19 VT 116 / Charlotte Rd Traffic Signal 2010 2,700 New signalized intersection between Mechanicsville Rd and CVU Rd (see Google Earth). Part of developer requirements. Capacity 20 VT 116 / Commerce St Traffic Signal 2010 ~3,000 21 VT 116 / CVU Road improvements - turn lanes or roundabout 2010 Node 559. Incease capacity to ~2,700 Node 477. Right turn lane from VT116 SB onto Silver St and realignment of intersection to T up 22 VT 116 / Silver St improvements 2010 with 116. No major change in capacity. I-89 exit 11 project, including northbound I-89 ramps/US2 intersection improvements, Nodes 687 and 1182. Single lane roundabout 23 and the development of a roundabout at VT 117/ US 2 intersection 2015 covering both of these nodes. South Burlington E-W connector roads: a) Swift St Extended between Dorset and VT116; b) Midland Ave between Spear and Dorset; c) Marceau Connector between Dorset and VT116 near Van Sicklen Rd See Dorset St Corridor Study (PDF Attached) all d) New Connector between Cider Mill and VT116 (just permitted - contact Lance capacities 2400 / unsignalized JBH approved list 24 Llewellyn for plan) 2015 on 10/26/07 25 US 2/Industrial Avenue - Intersection Reconstruction 2015 Node 432. Increase capacity by ~400 vph Node 641. New signalized intersection with 26 US 2/7 at VT 2A/Creek Farm 2015 capacity of 3,000 VT 117/Sand Hill Rd traffic signal with exclusive eastbound left turn lane on VT 117 and Change to signalized intersection with capacity 27 southbound left and right turn lanes. 2015 ~3,000 Code Alt 16A from Circ Williston EIS for Circ AB 28 Circumferential Highway Segments A and B 2015 identified in previous plans. 29 Champlain Parkway, Burlington; I-89 to Pine Sreet 2015 Add facility contemplated in EIS. 30 Champlain Parkway, Pine to Battery 2015 Add facility contemplated in EIS.
Exit 12B Alignment Study - Appendix C - Page 1 Effective ID Improvements Comments Date Improvements included in 2030 (open for travel by 2030): 1 Airport Dr. Extension to Airport Parkway, South Burlington 2020 New roadway with 1 lane in each direction. One lane in each direction. Code as previously 2 Circumferential Highway from Essex through Colchester (sections G through J) 2020 considered in 1986 FEIS. Increase capacity on VT 127 in Colchester between Heineburg Bridge over the Winooski and Lakeshore Dr according to recommendations in 3 Colchester VT 127 Arterial Project 2020 2001 Scoping Study. increase capacity by 100 - 200 vph along the 4 Corridor-wide signal coordination along VT 15 2020 corridor Expansion of the CCTA service area to Milton, Colchester and additional areas of Williston; commuter services to selected rural areas; increased transit service 5 frequencies 2020 See MTP Figure 5-2 for service descriptions 6 Five Corners 2020 no capacity change 7 I-89 Interchange at West Milton Road in Milton 2020 diamond interchange at W Milton Rd 8 Main Street at North and East Roads in Milton 2020 no capacity change 9 Extend Tilley Dr to Technology Park (Community Dr) 2020 I-89 widening to 3 lanes in each direction between Exit 13, South Burlington and 10 proposed VT289 in Colchester 2020 Increase I-89 to 3 lanes in each direction 11 Swift and Spear St intersection improvements 2020 check modeling for Dorset Corridor Study Node 1343. Current capacity should be ~3,000 - 12 US 2/7 at Hercules Drive 2020 now coded at 2,100 13 US 2/7 at I-89 Exit 16 2020 no capacity change 14 US 2/7 at LaFountain Street 2020 Increase capacity by ~200 vph Node 746. Current capacity should be ~3,000 - 15 US 2/7 at Rathe Road 2020 now coded at 2,100 16 US 2/7 at Spring Street in Winooski 2020 Increase capacity by ~200 vph 17 US 2/7 at Tigan Street 2020 Increase capacity by ~200 vph Node 1342. Current capacity should be ~4,000 - 18 US 2/7 at Watertower Hill 2020 now coded at 2,100
Check City Center EA for potential improvements. 19 US 2/Hinesburg Rd. (VT116) 2020 If none, assume capacity increase ~200 vph.
Check City Center EA for potential improvements. 20 US 2/Kennedy Dr. 2020 If none, assume capacity increase ~200 vph. 21 US 2/Shunpike Road 2020 Node 826. Increase capacity by ~200 vph. 22 US 7 at Main Street in Milton 2020 no capacity change 23 VT 117/ Skunk Hollow Road 2020 Node 602. Increase capacty by ~200 vph Node 1020 now coded as uncontrolled 10,000 capacity. Should be stop control class 2 with 2400 24 VT 117/North Williston Rd. 2020 capacity. 25 VT 15/East Spring Street 2020 no capacity change 26 VT 15/Essex Way 2020 no capacity change 27 VT 15/Lee River Road 2020 no capacity change 28 VT 15/Lime Kiln Road 2020 Increase capacity by ~200 vph Node 610. Change from stop control to signalized 29 VT 15/Sand Hill Road 2020 intersection with capacity of 3,000. 30 VT 289/VT 15 ramp 2020 no capacity change 1 lane in each direction connector to VT 289. 31 Allen Martin Parkway Connector 2025 Signalized intersection at VT289/ AMP. Node 1014. Change from stop control to 32 VT 15/Allen Martin Drive 2025 signalized with Allen Martin Pkwy in 2025
Exit 12B Alignment Study - Appendix C - Page 2
APPENDIX D – PIVOTING PROCESS METHODOLOGY
PIVOTING PROCESS
This memorandum describes a pivoting process used to estimate intersection turning movements for different transportation network and land use scenarios with traffic data generated by the Chittenden County MPO’s Regional Transportation Model. The transportation model is calibrated to existing conditions for the entire County and is often calibrated within corridors or sub-areas for analysis of specific projects. At these levels, the model is calibrated when it predicts traffic volumes on road segments that are reasonably close to actual traffic counts. Regional models are not calibrated to specific turning movements (left, through, right) at intersections because their values are often too small and the level of detail in the model is too coarse. Therefore, it is not advisable to use raw turning movement data from the model for analysis. However, for most transportation planning and engineering studies it is necessary to understand how the components of a scenario (new roads, road widening, new transit service, more development, etc) may affect the operation and design of intersections. The pivoting process is based on the concept that an existing ground count is the best starting point for estimating scenario traffic volumes at an intersection. It uses the change in volumes estimated by the model to adjust the ground counts. This approach ensures that intersection detail not included in the model (which does not always include all legs of an intersection) is carried forward in scenario volumes and corrects for any anomalies or significant differences between actual turning movements and the turning movements estimated by the model. There are three inputs to the pivoting process: Intersection turning movements from ground counts adjusted to the AM or PM peak hour for a base year (Base Ground); Model generated turning movements that correspond to the AM or PM peak hour ground counts (Base Model); and Model generated turning movement for the scenario being analyzed (Scenario Model). In its simplest form, the pivoting process adds the difference between the Scenario Model and Base Model runs to the ground counts as follows: Simple Pivot: Final Turning Movements = [Base Ground Turning Movement] plus [(Scenario Model Turning Movements) – (Base Model Turning Movements)] The “simple pivot” is used when each turning movement (left, through, right, etc) in the final turning movement is a positive number.
Pivoting Process Resource Systems Group, Inc.
October 2006 page 2
Scenarios that are modeled often reduce traffic through a particular intersection. In some cases, the reduction between the Scenario Model and Base Model volumes may be greater than the Base Ground count for a particular movement or for an entire approach. If the simple pivoting approach is used, the result is a negative turning movement and/or approach. The following methodologies are used for these cases. When a simple pivot results in a negative number for an entire approach, “proportional pivoting” is applied as follows: Proportional Pivot: Final Turning Movement = [Base Ground Turning Movement] multiplied by ratio of [Scenario Model Movement Volume/Base Model Movement Volume] When a simple pivot results in a negative number for a specific movement, but the entering volume for an entire approach is positive, “super pivoting” is applied to each movement on the approach as follows: Super Pivot: Final Turning Movement = [Movement Volume Calculated from Proportional Pivot] multiplied by ratio of [Simple Pivot Approach Volume/Proportional Pivot Approach Volume] The super pivot is applied to movements calculated using the proportional pivot because its value will always be positive. The super pivot adjustment maintains the total volume entering an approach developed with the simple pivot, but redistributes the traffic so that each movement remains positive.
APPENDIX E – SCENARIO VOLUME MAPS
Modified Diamond Interchange – 2018 PM Peak Hour Volumes
Hinesburg Road
I-89 NB On-Ramp 164 428 143 Tilley Drive 585 CK30 107 477 CK80 876 913 Kennedy Drive Kennedy 544 241 272 354 68 Community Drive Hinesburg Road I-89 NB Off-Ramp
Hinesburg Road 873 468 SB Off-Ramp
97 CK10 744 SB On-Ramp 960 257 Hinesburg Road
Standard SPUI & Simple Diamond – 2018 PM Peak Hour Volumes
Modified SPUI – 2018 PM Peak Hour Volumes
APPENDIX F – DESIGN ALTERNATIVES
APPENDIX G – COST ESTIMATES & ASSUMPTIONS Modified Diamond Modified Single Point Urban Interchange Estimate Methodology & Assumptions
Interstate 89 Proposed Exit 12B Date: Rev3-15-09 South Burlington, VT By: C. Mack Construction Cost Estimate - Alternative A - Modified Diamond Interchange Checked: M. Smith Section 1 : Earthwork Units Quantity Unit Price Item Total Clearing and Grubbing HA 8 10,600$ 84,800 Common Excavation CM 21100 9$ 189,900 Excavation of Surfaces and Pavement CM 1200 15$ 18,000 Solid Rock Excavation CM 12700 17$ 215,900 Import Borrow / Place Embankment CM 8400 22$ 184,800 Section 1 Subtotal = $ 693,400
Section 2 : Roadway Items Units Quantity Unit Price Item Total Asphalt Concrete MTON 3000 108$ 324,000 Base of Crushed Gravel (Fine Graded) CM 28600 40$ 1,144,000 Subbase of Dense Graded Sand CM 33700 22$ 741,400 Cast-in-Place Cement Concrete Curb, Type B M 900 96$ 86,400 Portland Cement Concrete Sidewalk, 5 inch SM 2900 76$ 220,400 Removal of Existing Guardrail M 300 8$ 2,400 Guardrail M 300 54$ 16,200 Chain Link Fence M 710 70$ 49,700 Utility Relocation LS 1 64,700$ 64,700 Miscellaneous Roadway Items LS 1 265,000$ 265,000 Section 2 Subtotal = $ 2,914,200
Section 3 : Drainage Items Units Quantity Unit Price Item Total Drainage Items LS 1 1,020,000$ 1,020,000 Section 3 Subtotal = $ 1,020,000
Section 4 : Environmental Items Units Quantity Unit Price Item Total Erosion and Sediment Control Plan LS 1 5,000$ 5,000 Monitoring Erosion and Sediment Control Plan HR 1000 44$ 44,000 Maintenance of Erosion and Sediment Control Plan LS 1 407,200$ 407,200 Environmental Mitigation LS 1 100,000$ 100,000 Wetland Restoration LS 1 100,000$ 100,000 Section 4 Subtotal = $ 656,200
Section 5 : Signage, Striping, Signals, and Lighting Units Quantity Unit Price Item Total Traffic Signs LS 1 145,800$ 145,800 Removing Signs LS 1 21,900$ 21,900 Striping LS 1 29,200$ 29,200 Traffic Signals EA 3 214,000$ 642,000 Lighting LS 1 291,500$ 291,500 Section 5 Subtotal = $ 1,130,400
Section 6 : Landscaping Units Quantity Unit Price Item Total Landscaping LS 1 145,800$ 145,800 Section 6 Subtotal = $ 145,800
Section 7 : Traffic Control Units Quantity Unit Price Item Total Interstate Crossover LS 1 500,000$ 500,000 Uniformed Traffic Officers LS 1 250,000$ 250,000 Flaggers HR 1700 21$ 35,700 Maintenance of Traffic LS 1 70,900$ 70,900 Portable Changeable Message Sign LS 1 254,000$ 254,000 Section 7 Subtotal = $ 1,110,600
Section 8 : Construction Operations Units Quantity Unit Price Item Total Field Office - Engineers MON 15 2,000$ 30,000 Testing Equipment - Bituminous LS 1 64,800$ 64,800 Mobilization/Demobilization LS 1 728,600$ 728,600 Section 8 Subtotal = $ 823,400
Section 9 : Structures Units Quantity Unit Price Item Total Removal of Existing Structure LS 1 600,000$ 600,000 New Bridge Structure & Piers SM 2100 4,000$ 8,400,000 Retaining Walls SM 0 800$ - Architectural Treatments LS 1 840,000$ 840,000 Section 9 Subtotal = $ 9,840,000 Estimated Construction Costs $ 18,334,000 Contingiency (15%)$ 2,750,100 Preliminary Engineering (20%) $ 3,666,800 Project Management (10%) $ 1,833,400 ROW Costs (estimated) $ - Construction Engineering (15%) $ 2,750,100 TOTAL PROJECT COSTS $ 29,334,400 Interstate 89 Proposed Exit 12B Date: Rev 3-19-08 South Burlington, VT By: C. Mack Construction Cost Estimate - Alternative B - Modified Single Point Urban Interchange Checked: M. Smith Section 1 : Earthwork Units Quantity Unit Price Item Total Clearing and Grubbing HA 9 10,600$ 95,400 Common Excavation CM 13500 9$ 121,500 Excavation of Surfaces and Pavement CM 1200 15$ 18,000 Solid Rock Excavation CM 8100 17$ 137,700 Import Borrow / Place Embankment CM 44900 22$ 987,800 Section 1 Subtotal = $ 1,360,400
Section 2 : Roadway Items Units Quantity Unit Price Item Total Asphalt Concrete MTON 2900 108$ 313,200 Base of Crushed Gravel (Fine Graded) CM 28500 40$ 1,140,000 Subbase of Dense Graded Sand CM 33300 22$ 732,600 Cast-in-Place Cement Concrete Curb, Type B M 940 96$ 90,240 Portland Cement Concrete Sidewalk, 5 inch SM 3500 76$ 266,000 Removal of Existing Guardrail M 300 8$ 2,400 Guardrail M 300 54$ 16,200 Chain Link Fence M 670 70$ 46,900 Utility Relocation LS 1 65,200$ 65,200 Miscellaneous Roadway Items LS 1 267,300$ 267,300 Section 2 Subtotal = $ 2,940,040
Section 3 : Drainage Items Units Quantity Unit Price Item Total Drainage Items LS 1 1,029,100$ 1,029,100 Section 3 Subtotal = $ 1,029,100
Section 4 : Environmental Items Units Quantity Unit Price Item Total Erosion and Sediment Control Plan LS 1 5,000$ 5,000 Monitoring Erosion and Sediment Control Plan HR 1000 44$ 44,000 Maintenance of Erosion and Sediment Control Plan LS 1 458,000$ 458,000 Environmental Mitigation LS 1 100,000$ 100,000 Wetland Restoration LS 1 100,000$ 100,000 Section 4 Subtotal = $ 707,000
Section 5 : Signage, Striping, Signals, and Lighting Units Quantity Unit Price Item Total Traffic Signs LS 1 294,100$ 294,100 Removing Signs LS 1 21,900$ 21,900 Striping LS 1 58,900$ 58,900 Traffic Signals EA 3 214,000$ 642,000 Lighting LS 1 294,100$ 294,100 Section 5 Subtotal = $ 1,311,000
Section 6 : Landscaping Units Quantity Unit Price Item Total Landscaping LS 1 294,100$ 294,100 Section 6 Subtotal = $ 294,100
Section 7 : Traffic Control Units Quantity Unit Price Item Total Interstate Crossover LS 1 500,000$ 500,000 Uniformed Traffic Officers LS 1 250,000$ 250,000 Flaggers HR 1700 21$ 35,700 Maintenance of Traffic LS 1 70,900$ 70,900 Portable Changeable Message Sign LS 1 254,000$ 254,000 Section 7 Subtotal = $ 1,110,600
Section 8 : Construction Operations Units Quantity Unit Price Item Total Field Office - Engineers MON 15 2,000$ 30,000 Testing Equipment - Bituminous LS 1 62,700$ 62,700 Mobilization/Demobilization LS 1 735,100$ 735,100 Section 8 Subtotal = $ 827,800
Section 9 : Structures Units Quantity Unit Price Item Total Removal of Existing Structure LS 1 600,000$ 600,000 New Bridge Structure & Piers SM 3700 4,000$ 14,800,000 Retaining Walls SM 800 800$ 640,000 Architectural Treatments LS 1 1,544,000$ 1,544,000 Section 9 Subtotal = $ 17,584,000 Estimated Construction Costs $ 27,164,040 Contingiency (15%)$ 4,074,606 Preliminary Engineering (20%) $ 5,432,808 Project Management (10%) $ 2,716,404 ROW Costs (estimated) $ - Construction Engineering (15%) $ 4,074,606 TOTAL PROJECT COSTS $ 43,462,464
MEMORANDUM
To: Project File From: Corey Mack, P.E. Subject: Exit 12B - Preliminary Cost Estimate Assumptions Date: 24 July 2008
This memorandum documents the procedures and assumptions used to quantify materials and unit costs for the Preliminary Cost Estimate prepared for the Exit 12B project in South Burlington, VT dated July 17, 2008. Two alternatives were studied for the proposed interchange on Interstate 89 (I-89) at State Route 116 (VT- 116), including the modified diamond alternative (Alternative A) and the modified single point urban interchange alternative (SPUI) (Alternative B). All calculations were performed in metric units. General Assumptions Right of Way costs and escalation rates were not taken into account. Right of Way was assumed to be prepared for this project separately and there were no associated costs for acquisition, easements, or support throughout the project limits. Furthermore, a separate study of the escalation rates of the materials and support costs is recommended to more accurately estimate the cost of the project. For items that require greater engineering study to accurately quantify, a reference interchange project was used to determine approximate cost relationships. The reference project included structure and ramp rehabilitation on Interstate 93 (I-93) at Rockingham Road near Derry, NH. The I-93/Rockingham Rd Interchange (IC) was chosen due to similarity in scope, size, and geography to the Exit 12B project. Section 1: Earthwork Clearing and Grubbing Areas of clearing and grubbing were calculated as the disturbed area of existing vegetation. The disturbed area was defined as a 5 m offset from the proposed edge of shoulder (ES). Infield grading areas were included in the calculation. A unit cost based on the impacted area was assumed from the I-93/Rockingham Rd IC bid prices. Common Excavation The common excavation was calculated by performing a simplified end-area method of volume determination for the proposed ramps and widened VT-116. All volumes of excavation were supplemented with additional volumes for the excavation required for the structural section of the roadway. A unit cost from the Vermont Agency of Transportation 2 Year Average Price List for Metric Projects (VTrans Price List) was assumed. Solid Rock Excavation Due to insufficient geotechnical information, the quantity of solid rock excavation was taken as 60% of the common excavation based on the I-93/Rockingham Rd Interchange(IC). A unit cost from the VTrans Price List was assumed. Import Borrow / Place Embankment The import borrow / place embankment quantity was calculated by performing a simplified end-area method of volume determination for the proposed ramps and widened VT-116. All volumes of import were reduced by the volume required for the structural section of the roadway. No excavated
Exit 12B Resource Systems Group, Inc. 24 July 2008 Page 2
material was assumed to be suitable for embankment. A unit cost from the VTrans Price List was assumed. Section 2: Roadway Items Asphalt Concrete The area of proposed roadway was calculated and a constant depth of six inches of asphalt concrete was assumed throughout the project. A volume and weight of asphalt was calculated, and a unit cost from the VTrans Price List was assumed. Base of Crushed Gravel (Fine Graded) The area of proposed roadway was calculated and a constant depth of 24 inches of crushed gravel was assumed as a base throughout the project. A volume of gravel was calculated, and a unit cost from the VTrans Price List was assumed. Subbase of Dense Graded Sand The area of proposed roadway was calculated and a constant depth of 35 inches of dense graded sand was assumed as a subbase throughout the project. A volume of sand was calculated, and a unit cost from the VTrans Price List was assumed. Cast-in-Place Concrete Curb, Type B Type B Cast-in-Place Concrete Curb was assumed along the length of VT-116. A unit cost from the VTrans Price List was assumed. Portland Cement Concrete Sidewalk, 5 inch An area of sidewalk was calculated and a unit cost from the VTrans Price List was assumed. Removal of Existing Guardrail A length of existing guardrail was assumed from the existing features and a unit cost from the VTrans Price List was assumed. Guardrail A length of guardrail was assumed based on proposed features and a unit cost from the VTrans Price List was assumed. Chain Link Fence Chain Link Fence was assumed to be required along I-89 where the disturbed area extended beyond the existing Right of Way. A unit cost from the VTrans Price List was assumed. Utility Relocation Based on the I-93/Rockingham Rd IC, the utility relocation costs were assumed to be 2.5% of the roadway costs. Miscellaneous Roadway Items The Miscellaneous Roadway Items are meant to cover the remaining specific roadway items not directly quantified. This was estimated to be 25% of the of all quantified roadway items based on the I-93/Rockingham Rd IC.
Exit 12B Resource Systems Group, Inc. 24 July 2008 Page 3
Section 3: Drainage Items Drainage Items Based on the I-93/Rockingham Rd IC, all drainage items were estimated to cost 35% of the total roadway items. Section 4: Environmental Items Erosion and Sediment Control Plan The erosion and sediment control plan was estimated based on the I-93/Rockingham Rd IC. Monitoring Erosion and Sediment Control Plan The number of hours for monitoring the erosion and sediment control plan was calculated per hectare of disturbed area for the I-93/Rockingham Rd IC. The hectares of disturbed area for the Exit 12B IC were then used to calculate the hours required for monitoring this project. The unit cost was estimated based on the I-93/Rockingham Rd IC. Maintenance of Erosion and Sediment Control Plan The cost for maintaining the erosion and sediment control plan was calculated per hectare of disturbed area for the I-93/Rockingham Rd IC. The hectares of disturbed area for the Exit 12B IC were then used to calculate the cost for maintaining this project. Environmental Mitigation The cost of environmental mitigation was conservatively based on the impacts of the project and subject to further input. Wetland Restoration The cost of wetland restoration was conservatively based on the impacts of the project and subject to further input. Section 5: Signage, Striping, Signals, and Lighting Traffic Signs The cost of traffic signs was estimated as 5% of the total roadway items based on the I- 93/Rockingham Rd IC. Due to the added complexity of signage for the SPUI, the estimate was increased to 10% of the total roadway items for Alternative B. Removing Signs The cost of removing traffic signs was estimated as 15% of the traffic signs based on the I- 93/Rockingham Rd IC. To maintain conformity between the alternatives, the cost of removing signs for Alternative B was assumed to equal that of Alternative A. Striping The cost of striping was estimated as 1% of the total roadway items based on the I-93/Rockingham Rd IC. Due to the added complexity of striping for the SPUI, the estimate was increased to 2% of the total roadway items for Alternative B.
Exit 12B Resource Systems Group, Inc. 24 July 2008 Page 4
Traffic Signals The number of traffic signals was calculated per alternative. A unit cost of traffic signals was calculated based on online literature from three states. Lighting The cost of lighting was estimated as 10% of the total roadway items based on the I-93/Rockingham Rd IC. Section 6: Landscaping Landscaping The cost of landscaping was estimated as 10% of the total roadway items based on the I- 93/Rockingham Rd IC. Section 7: Traffic Control Uniformed Traffic Officers The cost of uniformed traffic officers was calculated per month of construction activity for the I- 93/Rockingham Rd IC. The estimated length of construction activity for this project was then used to calculate the estimated cost of uniformed traffic officers. Flaggers The cost of flaggers was calculated per month of construction activity for the I-93/Rockingham Rd IC. The estimated length of construction activity for this project was then used to calculate the estimated cost of flaggers. Maintenance of Traffic The cost of maintenance of traffic was calculated per month of construction activity for the I- 93/Rockingham Rd IC. The estimated length of construction activity for this project was then used to calculate the estimated cost of traffic maintenance. Portable Changeable Message Signs The cost of portable changeable message signs was calculated per month of construction activity for the I-93/Rockingham Rd IC. The estimated length of construction activity for this project was then used to calculate the estimated cost of the message signs. Section 8: Construction Operations Field Office – Engineers The number of months of proposed construction activity were estimated and subject to change. A monthly unit cost for a field office for engineers was estimated based on the I-93/Rockingham Rd IC. Testing Equipment – Bituminous The cost of bituminous testing equipment was estimated per metric ton of asphalt concrete based on the I-93/Rockingham Rd IC. The total metric tonnage of asphalt concrete for this project was used to estimate the lump sum cost for bituminous testing equipment. Mobilization / Demobilization The cost of mobilization and demobilization was estimated as 25% of the total roadway items based on the I-93/Rockingham Rd IC.
Exit 12B Resource Systems Group, Inc. 24 July 2008 Page 5
Section 9: Structures Removal of Existing Structure The cost of removing the existing VT-116 overcrossing was estimated on existing bridge size and is subject to change. VT-116 Overcrossing Structure The cost of the proposed VT-116 overcrossing was estimated based on the area of the structure. A unit cost was applied per square meter of bridge area and is subject to change. Retaining Walls The cost of the proposed retaining walls was estimated based on the area of the structures. A unit cost was applied per square meter of wall area and is subject to change. Architectural Treatment The cost of architectural treatment was estimated to be 10% of the total structural cost due to the significance of the interchange as an entry point to the greater Burlington area.
END OF MEMO
References: Vermont Agency of Transportation 2 Year Average Price List for Metric Projects http://www.aot.state.vt.us/CostEstimating/documents/2YearMetricAveragedPriceList.pdf Interstate 93 at Rockingham Road Interchange Bid Results http://www.nh.gov/dot/bureaus/finance/bidresults/2008/documents/B14633E.TXT
APPENDIX H – DESIGN CRITERIA
Exit 12B - Ramp Design Criteria and notes RSG, Inc. 8/08, by mcs
All page references are from the 2004 AASHTO Green Book1
Consider 3 parts: Exits: exit terminal –> ramp –> ramp terminal Entrances: ramp terminal –> ramp –> entrance terminal
Alignment - See page 823 – “diagonal facilities”
Design Speed – see Ex. 10-56 and text on p. 825. - “not less than low range” - if Highway Design Speed is 70 mph (115 kph) => use 50 mph (80 kph) mid-range
Superelevation – assume 6% max - see exhibit 10-58 & p.144
Radius (see ex. 3-26) - Assume max super is 6% Min Radius for 45 mph (70 kph) is 643 ft. (184 m) - Assume max super is 4% Min Radius for 50 mph (80 kph) is 2300 ft. (690 m) - Avoid using min radius (p.229) - Lmin=15x design speed (English units, 10x if metric, p. 230)
Grade (p 828): - elevation gained typically in central portion - use 3-4% on downgrades if practical (truck considerations) - 5% max on upgrades (trucks) - Consider queue lengths on approach “platforms”
Vertical curvature (p. 271-275) - Crest curve Ex 3-72, V=50 mph, SSD=425 ft, K=84 (metric V=80, K=26) - Sag curve Ex 3-75, V=50 mph, SSD=425 ft, K=96 (metric V=80, K=30) - K=L/(G1-G2) - take care on vertical crests with sight distance
Cross slope – 1.5-2% for “moderate” rainfall - Max algebraic difference in cross slope (35 mph & over) 4-5%
1 Vermont State Standards, p. 10 – AASHTO design criteria rules
Exit 12B Design Criteria Aug 2008 Width – assume condition C. (p. 838) - Shoulders - for one-way operation - sum of left and right shoulder should not exceed 12 ft. (2-4 on left and 8-10 on right) - Width Case IIC - 20 ft. min, incl. shoulders. (no adj for radius with shoulders) - Width taper from ramp to accell lane 15:1 or flatter (Ex 10-62)
Terminals (p. 840) - for at-grade terminals see Chapter 9 of AASHTO Green Book - use “tapered” design where ramp provides adequate accell distance
Entrances (p. 845) - tapered design (SB entrance) o use 50:1 to 70:1 taper o use uniform taper where accell dist exceeds 1300 ft. - parallel design (NB entrance) o taper at end of entrance ramp = 300 ft. (p. 846) - acceleration distance (Ex 10-70) assume 70 mph design speed o from stop = 1620 ft (494 m) - gap acceptance (10-69) o Lg= 90-150m from nose, depending on nose width - adjust for grade(Ex 10-71), assume 50 mph o accell downgrade 3-4%, factor = 0.65 (use 0.75) o decell upgrade 5-6%, factor = 0.80 (use 0.90)
Exits (p. 849) - tapered (SB exit) o 2-5 deg divergence typical (ex 10-72) o caution with exits to right on right turns (p. 856) “tendency to exit inadvertently” o decell length (table 10-73) is 390 ft end of taper or where 12’wide to PC o accell from 0 to 45 (40 mph) = 560’, from 45 to 70 (53 mph) = 800, 1360 total - parallel (NB Exit)70 o decell from 70 (Va=58 mph) to 0 is 615 (187 m) - deceleration distance (Ex 10-70) assume 70 mph design speed o to stop = 615 ft (188 m) - adjust for grade(Ex 10-71) o decell upgrade 3-4%, factor = 0.9
Sideslopes - ensure soil stability is not an issue - use 1:4 min - 1:6 preferred
Exit 12B Design Criteria Aug 2008 Clearzone - 1:4 – backslope 30 ft, foreslope 34 ft. - 1:6 – backslope 30 ft, foreslope 46 ft.
Sight distance - “clear view of exit terminal, exit nose and gore” - Adjust all values with grades are greater than 3% by values in Ex. 9-53
SPUI see example page 787 & Ex 1023, p. 784
RAMP BY RAMP DESIGN NOTES: see ex. 10-72 (exit) 10-76(entrance)
All Ramps Vertical Curve: Kcrest = 84 (26), Ksag min = 96 (30 metric) Cross-section width – 10’-12’-4’ (3-3.6-1.2 m) Sideslope – 1:3 back, 1:4 fore (1:3 with guardrail where constrained) Design speed is 50 mph (80 kph) Tapers at end of accell 300 ft (90-100 m) Tapers at begin of decell 250 ft (75 m) Requ’d deceleration distance (70 mph - 0 stop) 615 feet (180m) Requ’d acceleration distance (0 stop to 70 mph) 1,620 feet (430m) Merge distance – max queue + 50x12=600’ (WS)
SB Exit Parallel deceleration exit design Grade in is +3%, ramp +5%, L-sag = 2 x 30=60m (min) ramp +5%, intersection approach +2%, L-crest = 3 x 26=78m (min)
SB Entrance Parallel acceleration entrance design 2 lanes required for double SB left off VT116 Grade in is -2% (intersection), ramp -3%, L-sag = 1 x 30=30m (min) ramp -3%, ramp terminal/interstate -2%, L-crest = 1 x 26=26m (min)
NB Exit Tapered deceleration exit design Grade in is +0-1%, ramp -0.5%, intersection approach +0.25%, L-sag/crest = negl. Requ’d deceleration distance to curve (70-45 mph curve) 390 feet (120m)
NB Entrance Parallel acceleration entrance design 2 lanes required for double NB left off VT116 Grade in is -2% (intersection), ramp -3.5%, L-sag = 1.5 x 30 = 45m (min) Grade of ramp -3.5%, ramp terminal/interstate -3% L-crest = negl.
Exit 12B Design Criteria Aug 2008
APPENDIX I – SUPPLEMENTAL MEMO
MEMORANDUM
To: Project Steering Committee From: Mark Smith, P.E. Subject: Exit 12B Alignment Study – Additional Analysis Date: 26 March 2009
This Supplemental Memorandum addresses comments received from VTrans concerning the Draft Final Report for the Exit 12B Conceptual Alignment Analysis. Specifically this memo provides the following additional information:
1. Traffic analysis results assuming the planned connector road from Tilley Drive to Technology Park is not built. This connection runs through an area with a stream in the watershed of an impaired waterway, extensive known wetlands and archaeological resources, and could be on a very different timeline than this project. A substantial amount of traffic was expected to use this connection, therefore the traffic volumes assumptions would be quite different without it. Scenarios studied in this new analysis include:
a. The simple diamond interchange configuration, which requires 2 new intersections on VT116. The northern intersection (at the northbound interstate ramps) would be quite close to the existing Tilley Drive intersection. This created signal timing, vehicle queuing and delay issues in the previous analysis, but was revisited with the revised traffic volumes.
b. The modified diamond configuration, which routes northbound I‐89 exit ramp traffic to Tilley Drive, thereby accessing VT116. This alternative only creates one new intersection with VT116 at the southbound ramps maintaining a more reasonable separation from the existing intersection at Tilley Drive. Two variations of this scenario were modeled:
i. With traffic signals at each intersection
ii. With roundabouts at each intersection
Project Memorandum Resource Systems Group, Inc. 3/26/2009 page 2
c. The modified single point diamond intersection (SPUI) configuration. A typical SPUI concept was used for this alternative, however the northbound entrance ramp would be moved north to originate at the existing Tilley Drive / VT116 intersection.
2. Revised cost estimates were developed which have been refined to align more closely with some examples suggested by VTrans. The two cost estimates are based on the two feasible alternatives (assuming the Tilley Drive Connector is in place):
a. The Modified Diamond
b. The Modified SPUI
REVISED TRAFFIC VOLUMES
The traffic volumes for the studied alternatives were revisited to assess the effect of eliminating the connection between Tilley Drive and Technology Park. These projected trips were rerouted to VT116 and the proposed interchange via Kennedy Drive. Tilley Drive traffic was estimated from the full build traffic analysis performed for the Tilley Subdivision by Hamlin Engineers in March of 2008. Modified volume diagrams and worksheets are attached.
TRAFFIC ANALYSIS RESULTS
Each alternative was assessed in Synchro (v7) for delay and volume/capacity ratios using the Highway Capacity Manual methodology (HCM), and five simulations were averaged from Simtraffic to assess expected queuing at each intersection. A summary of our findings from this analysis is listed below. Performance results are presented in Table 1.
Simple Diamond:
The proximity of the northbound ramps and the Tilley Drive intersection remains problematic, resulting in very long queues and delay southbound and westbound at Tilley Drive during the simulations. Note that HCM results for Delay and v/c do not reflect these issues because that methodology does not consider the interactions of closely spaced intersections.
Modified Diamond (with traffic signals), Modified Diamond (with roundabouts), Modified SPUI:
The traffic analysis shows that each of these alternatives performed well at all locations and would meet VTrans Level of Service (LOS) guidelines.
The roundabout alternative showed the least average delay and queuing.
The roundabout alternative requires slip lanes for right turns on 3 approaches, and one requires a double slip lane (the southbound off ramp). This type of geometry would be unusual and may present some concerns regarding safety.
Project Memorandum Resource Systems Group, Inc. 3/26/2009 page 3
Table 1: Traffic Analysis Results
2018 PM Peak Hour Simple Diamond1 Mod Diamond (Signals)Mod Diamond (Roundabouts) SPUI Link Max Max Max Max Signalized Intersections LOS Delay v/c Queue LOS Delay v/c Queue LOS Delay v/c Queue LOS Delay v/c Queue Length VT 116/Tilley Drive Overall B 15 C 30 B 13 B 17 Westbound Left (Tilley Drive) D 46 0.73 324 ‐‐‐0 B 14 0.47 82 ‐‐‐‐150 Westbound Thru (Tilley Drive ‐‐‐‐D 54 0.90 531 A 7 0.06 7 D 50 0.76 289 >2,000 Westbound Right (Tilley Drive) D 35 0.32 >1,000 C 32 0.68 438 A 5 0.51 109 C 35 0.19 238 >2,000 Northbound Left (VT 116) ‐‐‐‐D 36 0.86 283 B 12 0.39 90 ‐‐‐‐177 Northbound Thru (VT 116) A 8 0.56 143 A 4 0.46 186 A 3 0.39 89 B 10 0.68 209 177 Northbound Right (VT 116) A 4 0.03 42 ‐‐‐‐A 5 0.39 89 A 2 0.03 62 177 Southbound Left (VT 116) A 7 0.20 224 C 24 0.35 324 C 32 0.83 353 D 51 0.59 135 >2,000 Southbound Thru (VT 116) A 8 0.50 >1,000 C 32 0.84 724 C 24 0.83 374 A 8 0.50 656 >2,000 VT 116/NB Ramps Overall C 30 C32 Eastbound Left (SB Off‐Ramp) ‐‐‐‐ D370.29131 ‐ Westbound Left (NB Off‐Ramp) ‐‐‐‐ D490.74177 ‐ Westbound Thru (NB Off‐Ramp) E 63 0.83 375 ‐‐‐‐ ‐ Westbound Right (NB Off‐Ramp) D 37 0.17 329 ‐‐‐‐ ‐ Northbound Left (VT 116) D 43 0.85 419 D 43 0.77 156 369 Northbound Thru (VT 116) A 2 0.37 400 C 25 0.53 162 369 Southbound Left (VT 116) ‐‐‐‐ D 37 0.63 121 96 Southbound Thru (VT 116) C 29 0.87 160 B 18 0.51 122 96 VT 116/SB Ramps Overall C 21 B 19 A 8 0.60 0 ‐‐ Eastbound Left (SB Off‐Ramp) C 34 0.26 161 C 27 0.27 118 B 19 0.20 23 ‐‐‐‐ ‐ Eastbound Thru (SB Off‐Ramp D 53 0.79 165 D 47 0.81 165 B 11 0.20 23 ‐‐‐‐ ‐ Eastbound Right (SB Off‐Ramp) D 53 0.79 163 D 47 0.81 154 B 14 0.60 123 B 12 0.40 177 ‐ Northbound Thru/Right (VT 116) B 16 0.51 509 B 16 0.57 472 A 7 0.53 124 A <1 0.19 356 >2,000 Southbound Left (VT 116) B 12 0.57 304 A 6 0.60 314 A 9 0.42 0 ‐ ‐ ‐ ‐ 369 Southbound Thru (VT 116) A 5 0.76 395 A 7 0.75 387 A 3 0.42 0 A <1 0.28 64 369 Tilley Drive/NB Off Ramp Overall A A 8 0.33 0 Eastbound Thru (Tilley Drive) B 12 0.12 54 A 3 0.03 0 1,000 Westbound Thru (Tilley Drive) B 14 0.53 144 A 4 0.17 66 >2,000 Northbound Left (NB Off‐Ramp) A 8 0.51 254 B 11 0.33 35 ‐ 1 delay and LOS from the simulations were quite higher than those repoted here from the HCM analysis
Project Memorandum Resource Systems Group, Inc. 3/26/2009 page 4
RESULTING GEOMETRIC MODIFICATIONS
Given the change in traffic due to the elimination of the Tilley Drive connector, several geometric changes were possible to the intersection configurations compared to the alternatives with the connector. Specifically:
Modified diamond (Signals):
‐ Tilley Drive approach – reduce from 4 lanes to 2
‐ Northbound VT116 at Tilley Drive – eliminate exclusive right turn lane
Modified diamond (Roundabouts):
‐ Tilley Drive approach – reduce from 4 lanes to 2
‐ Northbound VT116 at Tilley Drive – eliminate exclusive right turn lane
‐ Both On‐Ramps ‐ Eliminate Left turn lanes – reducing bridge to 4 lanes
Single Point Urban Interchange:
‐ Tilley Drive approach – reduce from 3 lanes to 2
‐ Northbound VT116 – eliminate 1 thru lane on bridge
Required lane configurations are shown in the volume diagrams, attached.
COST ESTIMATES
The cost estimates were revised specifically to include the cost of building crossovers for each direction of interstate traffic on I‐89 during the proposed bridge work. In addition the bridge deck cost was increased to $375/s.f. ($4,000/s.m.). Detailed cost estimates are attached. The revised construction cost estimate totals (excluding right of way) are:
Modified Diamond – $29.3M
Modified SPUI – $43.5M
Note that the connector road was considered a separate project and was not included in the original estimates. The new traffic analysis provided herein shows some reduction in lane requirements may be realized if the Tilley Drive connector is not in place, however it is recommended the two cost estimates provided herein be used for worst case budgetary purposes.
END OF MEMO
Attachments:
Alternative Traffic Volumes & Required Geometry
- simple diamond configuration - modified diamond (signals) - modified diamond (roundabouts) - SPUI
Traffic Volume Worksheets
- simple diamond configuration - modified diamond - SPUI
Revised cost estimates
- modified diamond - SPUI
Simple Diamond (v2) - without Tilley / Tech Park Connector Road
2018 PM Peak Hour
Hinesburg Road 223 993 78 Tilley Drive Tilley
294 aj11 49 201
717 46 Hinesburg Road
Hinesburg Road 1193 NB On-Ramp
268 aj21 223 NB Off-Ramp NB 538 496 Hinesburg Road
Hinesburg Road 968 448 SB Off-Ramp
89 0 aj31 714 SB On-Ramp 946 261 Hinesburg Road Modified Diamond (signals) - without Tilley / Tech Park Connector Road
2018 PM Peak Hour
Hinesburg Road e I-89 NB On-Ramp 164 997 78 Tilley Drive 564 z25 25 48 z15 209 377 Community Drive
544 467 46NB On Ramp / Till 423 0 Hinesburg Road I-89 NB Off-Ramp
Hinesburg Road 905 468 SB Off-Ramp
97 z35 744 SB On-Ramp 960 257 Hinesburg Road Modified SPUI - without Tilley / Tech Park Connector Road
2018 PM Peak Hour
Hinesburg Road 223 993 78 Tilley Drive
294 aj10 49 201
717 46 Hinesburg Road
Hinesburg Road 1193 NB On-Ramp
268 aj20 223 NB Off-Ramp 538 496 Hinesburg Road
Hinesburg Road 968 448 SB Off-Ramp
89 aj30 714 SB On-Ramp 946 261 Hinesburg Road Modified Diamond (roundabouts) - without Tilley / Tech Park Connector Road
2018 PM Peak Hour
Hinesburg Road e I-89 NB On-Ramp 164 997 78 Tilley Drive 564 z25 25 48 z15 209 377 Community Drive
544 467 46NB On Ramp / Till 423 0 Hinesburg Road I-89 NB Off-Ramp
Hinesburg Road 905 468 NOTE: superimposed diagrams are the SB Off-Ramp geometric requirements from aaSidra 97 z35 744 SB On-Ramp 960 257 Hinesburg Road Estimated Full Buildout of Resulting Modified Modified Tilley Subdivision balancing Diamond Vols without Diamond Vols (& effect of no connector) connector 2018 2018 From: Final Report Oct 2008
Synchro Node redirected traffic redirected traffic see MCS hand calcs dated 4-11-08 Phase II traffic only
EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 1 Tilley Drive - NB Off-Ramp - Community Drive LT 0 0 354 0 LT 68 LT LT 0 0 423 0 So. Burlington, VT TH 477 876 0 0 TH TH TH 48 209 0 0 RT 0 0 68 0 1776 RT 68 RT 0 RT 0 0 0 0 680 Enter 477 876 423 0 1776 Enter 0 0 68 0 68 Enter 0 0 0 0 0 Enter 48 209 423 0 680 Exit 545 1231 0 0 1776 Exit 0 68 0 0 68 Exit 0 0 0 0 0 Exit 48 632 0 0 680 dev vols only dev vols + NB off ramp vols with redirected connector vols no change EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 2 VT 116 - NB On Ramp - Tilley Dr LT 0 913 544 143 LT 377.4 544 78 LT LT 0 377 544 78 South Burlington, VT TH 0 107 241 428 TH 25 467 1029 TH 0 -32 TH 0 25 467 997 RT 0 585 272 164 3397 RT 564 46 164 3293 RT -32 RT 0 564 46 164 3261 Enter 0 1605 1057 735 3397 Enter 0 966 1057 1270 3293 Enter 0 0 0 -32 -32 Enter 0 966 1057 1238 3261 Exit 415 815 826 1341 3397 Exit 124 733 1030 1406 3293 Exit 0 0 0 -32 -32 Exit 124 733 1030 1374 3261
EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 3 VT 116 - SB Ramps LT 97 0 0 468 LT LT LT 97 0 0 468 South Burlington, VT TH 0 0 960 873 TH TH 0 32 TH 0 0 960 905 RT 744 0 257 0 3398 RT 0 RT 32 RT 744 0 257 0 3430 Enter 841 0 1216 1341 3398 Enter 0 0 0 0 0 Enter 0 0 0 32 32 Enter 841 0 1216 1373 3430 Exit 724 0 1057 1617 3398 Exit 0 0 0 0 0 Exit 0 0 0 32 32 Exit 724 0 1057 1649 3430 Estimated Full Buildout of Simple Diamond Vols Resulting Simple Diamond Tilley Subdivision balancing PM Peak Hour Vols without connector (& effect of no connector) 2018 2018 From: Final Report Oct 2008 reference hand calcs dated 5-29-08 and DLHCE traffic report 3-24-08 Synchro Node lower vols entering / exiting Tilley dev vols only result in higher through vols sum of previous vols + change
EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 1 VT116/Hinesburg Rd-Tilley Dr. LT 893 146 LT 250 78 LT LT 0 250 0 78 So. Burlington, VT TH 476 545 TH 236 68 TH 5 -40 TH 0 0 717 1216 2/11/2008 RT 372 282 2714 RT 294 46 972 RT -35 RT 0 294 46 0 2601 2nd Monday Enter 0 1265 758 691 2714 Enter 0 544 282 146 972 Enter 0 0 5 -40 -35 Enter 0 544 763 1294 2601 RSG Count Exit 428 0 848 1438 2714 Exit 124 0 530 318 972 Exit 0 0 5 -40 -35 Exit 124 0 1011 1466 2601
EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 2 VT 116 - NB Ramps LT 0 223 538 0 LT LT LT 0 223 538 0 South Burlington, VT TH 0 0 512 1170 TH TH -16 23 TH 0 0 496 1193 RT 0 268 0 271 2982 RT 0 RT 7 RT 0 268 0 271 2989 Enter 0 491 1050 1441 2982 Enter 0 0 0 0 0 Enter 0 0 -16 23 7 Enter 0 491 1034 1464 2989 Exit 0 809 779 1393 2982 Exit 0 0 0 0 0 Exit 0 0 -16 23 7 Exit 0 809 763 1416 2989
EB WB NB SB EB WB NB SB EB WB NB SB EB WB NB SB 3 VT 116 - SB Ramps LT 89 0 0 448 LT LT LT 89 0 0 448 South Burlington, VT TH 0 0 939 937 TH TH 7 31 TH 0 0 946 968 RT 714 0 261 0 3388 RT 0 RT 38 RT 714 0 261 0 3426 Enter 803 0 1199 1385 3388 Enter 0 0 0 0 0 Enter 0 0 7 31 38 Enter 803 0 1206 1416 3426 Exit 709 0 1028 1652 3388 Exit 0 0 0 0 0 Exit 0 0 7 31 38 Exit 709 0 1035 1683 3426
NOTE: this estimate assumes all users of 12B will be use a different route to get to the interchange but does not estimate the use of alternate interchanges change due to moving NB Simple Diamond without on ramp (partially) to make 4- Resulting SPUI Diamond Connector way at Tilley Vols without connector 2018 2018
Synchro Node
EB WB NB SB EB WB NB SB EB WB NB SB 1 VT116/Hinesburg Rd-Tilley Dr. LT 0 250 0 78 LT -49 LT 0 201 0 78 So. Burlington, VT TH 0 0 717 1216 TH 49 -223 TH 0 49 717 993 2/11/2008 RT 0 294 46 0 2601 RT 223 0 RT 0 294 46 223 2601 2nd Monday Enter 0 544 763 1294 2601 Enter 0 0 0 0 0 Enter 0 544 763 1294 2601 RSG Count Exit 124 0 1011 1466 2601 Exit 0 271 0 -272 0 Exit 124 271 1011 1194 2601
EB WB NB SB EB WB NB SB EB WB NB SB 2 VT 116 - NB Ramps LT 0 223 538 0 LT LT 0 223 538 0 South Burlington, VT TH 0 0 496 1193 TH TH 0 0 496 1193 RT 0 268 0 271 2989 RT -271 -271 RT 0 268 0 0 2718 Enter 0 491 1034 1464 2989 Enter 0 0 0 -271 -271 Enter 0 491 1034 1193 2718 Exit 0 809 763 1416 2989 Exit 0 -271 0 0 -271 Exit 0 538 763 1416 2718
EB WB NB SB EB WB NB SB EB WB NB SB 3 VT 116 - SB Ramps LT 89 0 0 448 LT LT 89 0 0 448 South Burlington, VT TH 0 0 946 968 TH TH 0 0 946 968 RT 714 0 261 0 3426 RT 0 RT 714 0 261 0 3426 Enter 803 0 1206 1416 3426 Enter 0 0 0 0 0 Enter 803 0 1206 1416 3426 Exit 709 0 1035 1683 3426 Exit 0 0 0 0 0 Exit 709 0 1035 1683 3426
includes SB lefts includes EB lefts Interstate 89 Proposed Exit 12B Date: Rev3-15-09 South Burlington, VT By: C. Mack Construction Cost Estimate - Alternative A - Modified Diamond Interchange Checked: M. Smith Section 1 : Earthwork Units Quantity Unit Price Item Total Clearing and Grubbing HA 8 10,600$ 84,800 Common Excavation CM 21100 9$ 189,900 Excavation of Surfaces and Pavement CM 1200 15$ 18,000 Solid Rock Excavation CM 12700 17$ 215,900 Import Borrow / Place Embankment CM 8400 22$ 184,800 Section 1 Subtotal = $ 693,400
Section 2 : Roadway Items Units Quantity Unit Price Item Total Asphalt Concrete MTON 3000 108$ 324,000 Base of Crushed Gravel (Fine Graded) CM 28600 40$ 1,144,000 Subbase of Dense Graded Sand CM 33700 22$ 741,400 Cast-in-Place Cement Concrete Curb, Type B M 900 96$ 86,400 Portland Cement Concrete Sidewalk, 5 inch SM 2900 76$ 220,400 Removal of Existing Guardrail M 300 8$ 2,400 Guardrail M 300 54$ 16,200 Chain Link Fence M 710 70$ 49,700 Utility Relocation LS 1 64,700$ 64,700 Miscellaneous Roadway Items LS 1 265,000$ 265,000 Section 2 Subtotal = $ 2,914,200
Section 3 : Drainage Items Units Quantity Unit Price Item Total Drainage Items LS 1 1,020,000$ 1,020,000 Section 3 Subtotal = $ 1,020,000
Section 4 : Environmental Items Units Quantity Unit Price Item Total Erosion and Sediment Control Plan LS 1 5,000$ 5,000 Monitoring Erosion and Sediment Control Plan HR 1000 44$ 44,000 Maintenance of Erosion and Sediment Control Plan LS 1 407,200$ 407,200 Environmental Mitigation LS 1 100,000$ 100,000 Wetland Restoration LS 1 100,000$ 100,000 Section 4 Subtotal = $ 656,200
Section 5 : Signage, Striping, Signals, and Lighting Units Quantity Unit Price Item Total Traffic Signs LS 1 145,800$ 145,800 Removing Signs LS 1 21,900$ 21,900 Striping LS 1 29,200$ 29,200 Traffic Signals EA 3 214,000$ 642,000 Lighting LS 1 291,500$ 291,500 Section 5 Subtotal = $ 1,130,400
Section 6 : Landscaping Units Quantity Unit Price Item Total Landscaping LS 1 145,800$ 145,800 Section 6 Subtotal = $ 145,800
Section 7 : Traffic Control Units Quantity Unit Price Item Total Interstate Crossover LS 1 500,000$ 500,000 Uniformed Traffic Officers LS 1 250,000$ 250,000 Flaggers HR 1700 21$ 35,700 Maintenance of Traffic LS 1 70,900$ 70,900 Portable Changeable Message Sign LS 1 254,000$ 254,000 Section 7 Subtotal = $ 1,110,600
Section 8 : Construction Operations Units Quantity Unit Price Item Total Field Office - Engineers MON 15 2,000$ 30,000 Testing Equipment - Bituminous LS 1 64,800$ 64,800 Mobilization/Demobilization LS 1 728,600$ 728,600 Section 8 Subtotal = $ 823,400
Section 9 : Structures Units Quantity Unit Price Item Total Removal of Existing Structure LS 1 600,000$ 600,000 New Bridge Structure & Piers SM 2100 4,000$ 8,400,000 Retaining Walls SM 0 800$ - Architectural Treatments LS 1 840,000$ 840,000 Section 9 Subtotal = $ 9,840,000 Estimated Construction Costs $ 18,334,000 Contingiency (15%)$ 2,750,100 Preliminary Engineering (20%) $ 3,666,800 Project Management (10%) $ 1,833,400 ROW Costs (estimated) $ - Construction Engineering (15%) $ 2,750,100 TOTAL PROJECT COSTS $ 29,334,400 Interstate 89 Proposed Exit 12B Date: Rev 3-19-08 South Burlington, VT By: C. Mack Construction Cost Estimate - Alternative B - Modified Single Point Urban Interchange Checked: M. Smith Section 1 : Earthwork Units Quantity Unit Price Item Total Clearing and Grubbing HA 9 10,600$ 95,400 Common Excavation CM 13500 9$ 121,500 Excavation of Surfaces and Pavement CM 1200 15$ 18,000 Solid Rock Excavation CM 8100 17$ 137,700 Import Borrow / Place Embankment CM 44900 22$ 987,800 Section 1 Subtotal = $ 1,360,400
Section 2 : Roadway Items Units Quantity Unit Price Item Total Asphalt Concrete MTON 2900 108$ 313,200 Base of Crushed Gravel (Fine Graded) CM 28500 40$ 1,140,000 Subbase of Dense Graded Sand CM 33300 22$ 732,600 Cast-in-Place Cement Concrete Curb, Type B M 940 96$ 90,240 Portland Cement Concrete Sidewalk, 5 inch SM 3500 76$ 266,000 Removal of Existing Guardrail M 300 8$ 2,400 Guardrail M 300 54$ 16,200 Chain Link Fence M 670 70$ 46,900 Utility Relocation LS 1 65,200$ 65,200 Miscellaneous Roadway Items LS 1 267,300$ 267,300 Section 2 Subtotal = $ 2,940,040
Section 3 : Drainage Items Units Quantity Unit Price Item Total Drainage Items LS 1 1,029,100$ 1,029,100 Section 3 Subtotal = $ 1,029,100
Section 4 : Environmental Items Units Quantity Unit Price Item Total Erosion and Sediment Control Plan LS 1 5,000$ 5,000 Monitoring Erosion and Sediment Control Plan HR 1000 44$ 44,000 Maintenance of Erosion and Sediment Control Plan LS 1 458,000$ 458,000 Environmental Mitigation LS 1 100,000$ 100,000 Wetland Restoration LS 1 100,000$ 100,000 Section 4 Subtotal = $ 707,000
Section 5 : Signage, Striping, Signals, and Lighting Units Quantity Unit Price Item Total Traffic Signs LS 1 294,100$ 294,100 Removing Signs LS 1 21,900$ 21,900 Striping LS 1 58,900$ 58,900 Traffic Signals EA 3 214,000$ 642,000 Lighting LS 1 294,100$ 294,100 Section 5 Subtotal = $ 1,311,000
Section 6 : Landscaping Units Quantity Unit Price Item Total Landscaping LS 1 294,100$ 294,100 Section 6 Subtotal = $ 294,100
Section 7 : Traffic Control Units Quantity Unit Price Item Total Interstate Crossover LS 1 500,000$ 500,000 Uniformed Traffic Officers LS 1 250,000$ 250,000 Flaggers HR 1700 21$ 35,700 Maintenance of Traffic LS 1 70,900$ 70,900 Portable Changeable Message Sign LS 1 254,000$ 254,000 Section 7 Subtotal = $ 1,110,600
Section 8 : Construction Operations Units Quantity Unit Price Item Total Field Office - Engineers MON 15 2,000$ 30,000 Testing Equipment - Bituminous LS 1 62,700$ 62,700 Mobilization/Demobilization LS 1 735,100$ 735,100 Section 8 Subtotal = $ 827,800
Section 9 : Structures Units Quantity Unit Price Item Total Removal of Existing Structure LS 1 600,000$ 600,000 New Bridge Structure & Piers SM 3700 4,000$ 14,800,000 Retaining Walls SM 800 800$ 640,000 Architectural Treatments LS 1 1,544,000$ 1,544,000 Section 9 Subtotal = $ 17,584,000 Estimated Construction Costs $ 27,164,040 Contingiency (15%)$ 4,074,606 Preliminary Engineering (20%) $ 5,432,808 Project Management (10%) $ 2,716,404 ROW Costs (estimated) $ - Construction Engineering (15%) $ 4,074,606 TOTAL PROJECT COSTS $ 43,462,464