NCDOT STIP I-4400/4700 PURPOSE AND NEED TRAFFIC ANALYSIS - ADDENDUM I-26 Widening – Buncombe and Henderson Counties PREPARED FOR: North Carolina Department of Transportation Project Development & Environmental Analysis Branch PREPARED BY: HNTB North Carolina, PC 343 East Six Forks Road Suite 200 Raleigh, NC 27609 NCBELS License #: C-1554 October 2014 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum EXECUTIVE SUMMARY 1. Introduction HNTB North Carolina, PC has been contracted by the North Carolina Department of Transportation (NCDOT), to develop base and future year traffic capacity analyses for NCDOT State Transportation Improvement Program (STIP) Project I-4400/I-4700, I-26 Widening in Buncombe and Henderson Counties. The analyses for the base and future design year scenarios will be used to develop the environmental documentation required by the National Environmental Policy Act (NEPA). For the purposes of the environmental document, it was decided in a project scoping meeting on August 15, 2012 and through coordination with NCDOT that the base year scenario would use a base year of 2011 and the future design year scenario would be for the year 2040. In this meeting, a project study area was also defined that would satisfy the requirements of NEPA and potential Interchange Modification Report (IMR) requirements for the Federal Highway Administration (FHWA). Separate No-Build and Build Alternative traffic capacity analyses were conducted for both the 2011 base year and 2040 design year. Figure 1 shows the project study area for the traffic analyses. Appendix A contains all figures described in this report. The NCDOT STIP I-4400/I-4700 Purpose and Need Traffic Analysis Technical Memorandum was completed by HNTB in September 2013 and studied three alternatives: the No-Build Alternative, the Build 6-Lane alternative, and the Build 8-Lane Alternative. The September 2013 report recommended that consideration should be made in the design of I-4400/I-4700 to examine an eight-lane facility for a portion of the I-26 corridor and transition to a six-lane facility for the remainder of the corridor. Based on the 2040 design year freeway system analysis results, the most reasonable transition between a six-lane widening and eight-lane widening is at the current US 25 (Asheville Highway) interchange, with eight lanes required north of this location and six lanes required south of the interchange. Therefore, this memorandum serves as an addendum to the NCDOT STIP I-4400/I-4700 Purpose and Need Traffic Analysis Technical Memorandum (HNTB, September 2013) and compares the No-Build alternative from the September 2013 report to an additional Build Alternative: the Build 8/6-Lane Combination alternative. With this additional study, there are three Build Alternatives that are being studied in the NEPA process, the two from the September 2013 report (Build 6-Lane and Build 8-Lane alternatives) and the Build 8/6-Lane Combination alternative from this addendum report. This analysis addendum also contains detailed traffic microsimulation analyses for two locations along the project study area corridor. Initial results from the September 2013 technical memorandum indicated that interchange improvements will be necessary at the US 25 (Asheville Highway) interchange to provide adequate traffic operations in this vicinity. Results also indicated that additional detailed study was necessary for the I-26 southbound segment between the Upward Road and US 25 (Flat Rock) interchanges to determine if proposed Build – 6 Lane and Build – 8 Lane designs would provide adequate traffic operations at this project terminus. 2. Existing Conditions The existing geometrics, intersection traffic control, and speed limits for existing freeway network and roadways in the study area are shown schematically in Figures 2.1 to 2.3. Refer to Executive Summary Section 2 of NCDOT STIP I-4400/I-4700 Purpose and Need Traffic October 2014 ES-2 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Analysis Technical Memorandum (HNTB, September 2013) for detailed information on existing conditions in the project study area. 3. Capacity Analysis Methodology Per standards for the preparation of capacity analyses for TIP projects used by the NCDOT Congestion Management Section, and to ultimately satisfy requirements of an IMR for the FHWA, the I-4400/I-4700 project study area was analyzed using methodologies set forth in the Highway Capacity Manual 2010 (Transportation Research Board, December 2010) and the accompanying Highway Capacity Software 2010 (HCS Version 6.41) for freeway facilities and unsignalized intersections. Signalized intersections were analyzed in Synchro Professional Version 7. Results for AM and PM peak hour timeframes are given as a Level-of-Service (LOS) for segments of freeway and intersections that correspond to a letter grade of LOS A through LOS F. As noted in the September 2013 traffic analysis technical memorandum, in general, LOS D is the minimum threshold for acceptable peak hour traffic operations on the freeway segments and study area intersections, and was used as a benchmark in determining the appropriate functional design geometrics for the 2040 analysis year. Additional traffic microsimulation studies contained in this analysis addendum were completed using the Caliper TransModeler software package Version 3.0. Methodologies for traffic microsimulation development, calibration, and validation conform to NCDOT and FHWA standards and are described in detail in Sections 9 and 10 of this report. 4. Development of Alternatives Two alternatives were studied in this addendum report: the No-Build Alternative and the Build 8/6-Lane Combination alternative. The No-Build Alternative assumes no changes to the project study corridor, other than the proposed Balfour Parkway interchange (FS 1214B), current capacity improvements at the Upward Road interchange (STIP R-4430), and basic traffic signal retiming by the 2040 design year as indicated in the September 2013 capacity analysis study. The Build 8/6 Lane Combination Alternative studied in this addendum analysis assumes mainline widening of the existing I-26 facility with two additional lanes in each direction between the I-40/I-240/I-26 system interchange and US 25 (Asheville Highway) and one additional lane in each direction between US 25 (Asheville Highway) and the US 25 system interchange. This alternative was specifically developed to address future capacity needs as determined in the original traffic analysis technical memorandum. This addendum analysis also addresses potential improvements and design considerations at two locations along the I-26 project study corridor. Initial capacity analysis results indicate the need for additional interchange improvements at the I-25/US 25 (Ashville Highway) service interchange. Initial results were also inconclusive as to the effects of lane drops for I-26 southbound at the southern project termini between the Upward Road interchange and the US 25 system interchange. 5. 2011 Base Year/2040 Design Year Traffic Volume Development Peak hour traffic volume estimates for the 2011 base year and 2040 design year were developed as previously indicated in Executive Summary Section 5 of the NCDOT STIP I- 4400/I-4700 Purpose and Need Traffic Analysis Technical Memorandum (HNTB, September 2013). Because the Build 8/6 Lane Combination Alternative would exhibit the potential to experience slightly different peak hour traffic volumes than the original Build-6 Lane and Build-8 Lane October 2014 ES-3 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Alternatives, NCDOT TPB produced a traffic forecast expansion for this Alternative, submitted December 16, 2013. Traffic volumes for the combination alternative were updated in all traffic analyses presented in this technical memorandum addendum. 6. Capacity Analysis Results Freeway Operations The results from the HCS FreeVal analysis, shown in Table ES-2 for freeway segments, indicate that traffic operations along northbound and southbound I-26 in the project study area are mostly acceptable (LOS D or better) for 2011 base analysis year No-Build conditions, with the exception of 16 segments north of the NC 280 interchange that operate at a LOS E, given the existing traffic forecast peak hour volumes and existing geometrics. The proposed capacity expansion of a combination of six and eight travel lanes eliminates these deficiencies in the 2011 base year. There will be several changes to the I-26 freeway segments due to the future Balfour Parkway interchange in the 2040 design year. Table ES-2. I-4400/4700 Freeway Capacity Analysis Summary Number of Freeway Segments Operating at Given LOS Analysis Scenario in at Least One AM or PM Peak Hour Year LOS A LOS B LOS C LOS D LOS E LOS F No-Build 0 16 36 16 16 0 2011 Build – 8/6 Lane 1 64 18 1 0 0 Combination No-Build 0 0 15 19 53 7 2040 Build – 8/6 Lane 0 0 42 52 0 0 Combination In general, the additional capacity provided by the 8/6 Lane Combination Alternative will provide improved freeway operations along the I-26 corridor in the 2040 design year, even though traffic forecasts for the build alternative project daily traffic volumes increase along the facility because of the capacity expansion. In the 2040 design year, 60 of the 94 analyzed freeway segments are projected to be at or over capacity in the No-Build Alternative. The Build – 8/6 Lane Combination Alternative eliminates these deficiencies in the 2040 design year. Additional traffic microsimulation models were developed for this addendum study to verify and further explore the potential causes of the reported deficient LOS E/F freeway segments for the Build – 8 Lane and Build – 6 Lane Alternatives in the original traffic analysis technical memorandum. Intersection Operations The results from the HCS (unsignalized) and Synchro (signalized) intersections analyses indicate that there are some traffic congestion issues at interchange ramp terminals in the project study area in the 2011 base year, with these issues projected to increase in the 2040 design year peak hours. The Build 8/6 Lane Combination Alternative provides additional interstate mainline capacity, but was not studied, for the purposes of this report, to add improvements to mitigate any interchange ramp terminal operational issues except for the service interchange at US 25 (Asheville Highway), where traffic microsimulation was utilized to evaluate four potential interchange improvement designs at this location. Table ES-3 provides intersection capacity analysis results for all signalized and unsignalized intersections in the project study area for the 2011 and 2040 analysis years. October 2014 ES-4 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Table ES-3. 2011 Base Year / 2040 Design Year Intersection Capacity Analysis Results 2011 Base Year 2040 Design Year Peak Intersections No-Build Build 8/6 Lane No-Build Build 8/6 Lane Hour LOS Delay LOS Delay LOS Delay LOS Delay AM C 21.8 C 32.0 C 30.5 D 35.1 1) NC 146 SPUI Ramps PM C 21.5 C 32.0 C 30.0 C 33.7 2) US 25 (Asheville Highway) AM D 47.1 C 21.8 F 161.1 F 126.7 Northbound Ramps PM E 77.6 D 41.9 F 174.5 F 151.5 3) US 25 (Asheville Highway) AM F 162.9 F 102.0 F 265.6 F 241.3 Southbound Ramps PM D 50.2 E 57.6 F 259.8 F 217.3 4) Future Balfour Parkway AM N/A N/A N/A N/A B 18.6 C 27.3 Northbound Ramps PM N/A N/A N/A N/A B 16.0 C 27.1 5) Future Balfour Parkway AM N/A N/A N/A N/A B 15.8 B 18.7 Southbound Ramps PM N/A N/A N/A N/A B 18.3 C 23.8 6) US 64 & AM E 65.2 D 37.7 E 62.7 E 76.0 Francis Road/Sugarloaf Road PM D 41.1 C 33.7 D 52.2 E 59.3 7) US 64 & AM B 13.9 B 11.2 B 15.2 B 16.4 I-26 Southbound Off Ramp PM A 9.1 B 10.2 B 11.9 B 13.5 8) US 64 & Carolina Village AM D 49.8 C 33.2 F 107.6 F 107.4 Road / Orr’s Camp Road PM D 47.5 D 41.0 F 106.1 F 104.7 9) Upward Road AM C 22.3 C 22.7 C 32.2 C 30.3 Northbound Ramps PM D 35.9 D 39.0 C 28.7 C 28.6 10) Upward Road AM C 31.4 C 34.6 C 23.6 C 29.7 Southbound Ramps PM C 22.7 C 24.8 B 19.8 C 24.5 11) Holbert Cove Road AM B 12.6 B 12.6 B 14.2 B 14.6 Northbound Ramps* PM B 12.2 B 12.2 B 15.0 B 14.5 12) Holbert Cove Road AM B 11.2 B 11.2 B 13.3 B 13.3 Southbound Ramps* PM B 11.0 B 11.0 B 13.0 B 13.0 Delay Measured in Seconds Per Vehicle. N/A - Not Applicable, i.e. intersection is non-existent * - LOS/Delay Data is for worst-case critical stop-controlled movement BOLD/ITALIC = Intersection/Approach/Movement that has Operational Deficiencies (LOS E or F) 7. Microsimulation Analysis I-26/US 25 (Asheville Highway) Interchange Existing Base Year 2011 AM and PM peak hour microsimulation models of the US 25 (Asheville Highway) service interchange were developed using the TransModeler software package. After successfully calibrating the models to existing field observed conditions, the model networks were modified to test four (4) proposed initial design concepts – a diverging diamond interchange (DDI), a displaced left-turn Interchange (DLT), a standard partial cloverleaf, and a modified partial cloverleaf containing some design exceptions that allow a smaller interchange footprint. Measures of Effectiveness (MOEs) such as travel speeds, delays, and queues were extracted from the models (averages of 10 model runs for each scenario), and a comparison of the No- Build Alternative and Build Alternatives for system operations is presented in Table ES-4. October 2014 ES-5 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Table ES-4. 2011 and 2040 No-Build to Build System-Level Comparison Percent Improvement over No-Build Alternative Vehicle Miles Vehicle Hours Mean System Total System Analysis Build Alternative Traveled (VMT) Traveled (VHT) Speed (mph) Delay (Hours) Year AM PM AM PM AM PM AM PM Peak Peak Peak Peak Peak Peak Peak Peak 2011 9% 21% -14% -8% 26% 30% -44% -38% DDI 2040 92% 78% -77% -73% 468% 380% -85% -83% 2011 9% 21% -20% -20% 35% 50% -56% -63% DLT 2040 97% 84% -85% -84% 731% 686% -94% -95% 2011 13% 26% -18% -15% 37% 48% -60% -62% Partial Cloverleaf 2040 105% 90% -87% -85% 873% 735% -97% -96% Partial Cloverleaf 2011 11% 24% -19% -16% 36% 47% -60% -63% (Design Exception) 2040 103% 88% -87% -85% 870% 743% -97% -96% The data, and corresponding corridor and intersection-level analyses indicates that all four design alternatives improve overall system and corridor performance in both peak hours for the vehicle hours traveled, speed, and delay MOEs. However, the two partial cloverleaf designs offer the most operational benefits, followed by the DLT and finally, the DDI. Based solely on operational performance, the partial cloverleaf designs are recommended for further environmental study to assess their impacts. I-26 Southbound Merge/Diverge Area The TransModeler software package was used to develop traffic microsimulation networks of the I-26 southbound corridor between the Upward Road southbound on-ramp and the US 25 (Flat Rock) off-ramp. This analysis was necessary to verify the initial FreeVal results from the original Purpose and Need Traffic Analysis Technical Memorandum. FreeVal results indicated that the Build Alternatives performed poorly at the southern terminus of the project for southbound travel in the AM peak hour, with the 8-Lane Alternative performing worse than the 6-Lane alternative. Since FreeVal inputs cannot explicitly handle the actual geometrics of the 8- Lane design (with inner lane drop), the area was tested in microsimulation. 2040 design year microsimulation results for all the Build Alternatives indicate that this area of I- 26 should operate much better than the initially reported FreeVal data indicated. Thus, any of the Build Alternatives should provide adequate traffic operations for this particular area of the project. 8. Summary and Recommendations The I-4400/I-4700 traffic capacity analysis addendum was completed to evaluate existing and future peak hour traffic operations along I-26 and its study area interchanges to determine if a hybrid combination study alternative meets the purpose and need for the project. Three alternatives were analyzed in the original September 2013 study – the No-Build Alternative and the Six and Eight-Lane Widening Build Alternatives, and two alternatives were analyzed in this addendum study – the No-Build Alternative and an Eight/Six Lane Combination Alternative. Refer to Executive Summary Section 8 of the NCDOT STIP I-4400/I-4700 Purpose and Need October 2014 ES-6 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Traffic Analysis Technical Memorandum (HNTB, September 2013) for the summary and recommendations pertaining to the original Six and Eight-Lane Widening Build Alternatives. The following points summarize the results contained in this addendum report, along with recommendations for two specific areas studied using traffic microsimulation software. • I-26 Mainline Analysis The Build – 8/6 Lane Combination alternative assumes that I-26 will be widened for an additional travel lane in each direction from the I-40/I-240/I-26 system interchange to the US 25 (Asheville Highway) interchange, and two additional travel lanes in each direction from the US 25 (Asheville Highway) interchange to the US 25 system interchange. No specific design details related to which side of the existing facility would be widened were assumed, nor were any improvements assumptions made for necessary changes to existing overpass / underpass y-line facilities or interchange ramp terminals, except as described below. Proposed design changes to existing ramp acceleration/deceleration lane lengths along I-26 were included for the Build alternative in this study. Freeway operations results for this alternative indicate that it would mitigate all 2011 base year operational deficiencies, along with providing adequate capacity for all freeway segments along the corridor in the 2040 design year in both peak hours. • US 25 (Asheville Highway) Interchange Improvements Analysis The No-Build Alternative has major operational issues in the 2040 design year, effectively completely grid-locking the model network. All four Build alternatives offer operational improvement in both the 2011 Base Year and 2040 Design Year, though the partial cloverleaf options provide the most operational benefits. • I-26 Southbound Southern Project Termini Analysis Generally, all three I-26 design alternatives improve freeway densities in this section by 50 percent or more compared to the No-Build existing freeway and on-ramp/off-ramp configuration. Density values reported from the Build alternative simulation runs, if compared to HCM methodology LOS ranges and thresholds for basic freeway, ramp merge/diverge segments, would equate to a LOS D or better in both peak hours in the 2040 design year. Therefore, any of the I-26 Build Alternative current conceptual designs should provide adequate peak hour traffic operations in the 2040 design year peak hours for this segment of I-26. This also serves to verify that the initial 2040 design year capacity analysis results from FreeVal are not valid for this area. One additional recommendation, based on freeway and intersection capacity analysis results found in the original I-4400/I-4700 capacity analysis report, and remaining unchanged from findings in this study include: • Additional improvements may also be needed for the US 64 corridor signalized intersections adjacent to the I-26 interchange to prevent congestion impact to the interchange area. These improvements may not necessarily be part of alternative designs for the I-4400/I- 4700 project. October 2014 ES-7 NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum Table of Contents APPENDIX LIST/LIST OF FIGURES .......................................................................................... ii LIST OF TABLES ....................................................................................................................... ii 1. Introduction .......................................................................................................................... 1 2. Existing Conditions ............................................................................................................. 2 3. Capacity Analysis Methodology .......................................................................................... 2 3.1 Freeway Analysis Methodology ................................................................................ 4 3.2 Signalized Intersection Analysis Methodology .......................................................... 4 3.3 Unsignalized Intersection Analysis Methodology ...................................................... 5 3.4 Traffic Microsimulation Methodology ......................................................................... 5 4. Development of Alternatives ................................................................................................ 5 4.1 No-Build Alternative .................................................................................................. 6 4.2 Build Alternative – Widen I-26 to Eight/Six Lanes ..................................................... 6 5. 2011 Base Year / 2040 Design Year Traffic Volume Development ..................................... 6 6. 2011 Base Year Capacity Analysis Results ......................................................................... 7 6.1 2011 Freeway Segment Results ............................................................................... 7 6.1.1 2011 No-Build Alternative Scenario Results ............................................... 7 6.1.2 2011 Build – 8/6 Lane Combination Alternative Scenario Results .............. 7 6.2 2011 Base Year Intersection Capacity Analysis Results ......................................... 10 6.2.1 2011 No-Build Alternative Scenario Results ............................................. 10 6.2.2 2011 Build – 8/6 Lane Combination Alternative Scenario Results ............ 10 7. 2040 Design Year Capacity Analysis Results ................................................................... 13 7.1 2040 Freeway Segment Analysis Results ............................................................... 13 7.1.1 2040 No-Build Alternative Scenario Results ............................................. 13 7.1.2 2040 Build – 8/6 Lane Combination Alternative Scenario Results ............ 14 7.2 2040 Design Year Intersection Capacity Analysis Results ...................................... 17 7.2.1 2040 No-Build Alternative Scenario Results ............................................ 20 7.2.2 2040 Build – 8/6 Lane Combination Alternative Scenario Results ............ 20 8. I-26 Failure Year Analysis .................................................................................................. 21 9. I-26/US 25 (Asheville Highway) Interchange Alternatives Operations Analysis ............ 22 9.1 Preliminary Alternatives Studied ............................................................................. 22 9.2 Measures of Effectiveness ...................................................................................... 23 9.3 Microscopic Traffic Simulation Calibration .............................................................. 24 9.3.1 2011 Base Year No-Build Calibration Results .......................................... 25 9.4 Alternative Analysis Results.................................................................................... 26 9.4.1 2011 Base Year Alternative Scenario Results .......................................... 26 9.4.2 2040 Design Year Alternative Scenario Results ....................................... 29 October 2014 i NCDOT STIP I-4400/I-4700: I-26 Widening (Buncombe & Henderson Counties) Purpose and Need Traffic Analysis Technical Memorandum Addendum 10. I-26 Southbound Project Termini Operations Analysis ................................................. 32 10.1 Preliminary Alternatives Studied ........................................................................... 32 10.2 Measures of Effectiveness and Calibration ........................................................... 32 10.3 Analysis Results ................................................................................................... 32 10.3.1 2011 Base Year No-Build Scenario Results ........................................... 33 10.3.2 2040 Design Year Alternative Scenario Results ..................................... 33 11. Conclusions and Recommendations .............................................................................. 35 11.1 Freeway/Interchange Ramp Terminal Operations ................................................. 35 11.2 US 25 (Asheville Highway) Service Interchange Analysis ..................................... 36 11.3 I-26 Southbound Termini Analysis ........................................................................ 37 APPENDICES A. Figures B. Updated Traffic Forecast for Build – 8/6 Lane Combination Alternative C. FreeVal Freeway System Analysis Output D. Synchro Signalized Analysis Output E. Highway Capacity Software Unsignalized Analysis Output F. 2040 Peak Hour Breakout Spreadsheets G. I-26 Mainline Failure Year Analysis H. US 25 Asheville Highway and I-26 Interchange Field Speed Distributions and Travel Time Figures 1) ........... Traffic Analysis Study Area 2.1-2.3) .. Existing No-Build Laneage & HCM Segment/Intersection ID Numbers 3.1-3.3) .. 2011 Base Year No-Build Laneage, Volumes, & LOS 4.1-4.3) .. 2011 Base Year Build 8/6 Lane Combination Alternative Laneage, Volumes, & LOS 5.1-5.2) .. 2040 Design Year Laneage & HCM Segment/Intersection ID Number Changes 6.1-6.4) .. 2040 Design Year No-Build Laneage, Volumes, & LOS 7.1-7.4) .. 2040 Design Year Build 8/6 Lane Combination Alternative Laneage, Volumes, & LOS 8.1-8.10) US 25 Asheville Highway Interchange Alternatives TransModeler Analysis 9.1) ........ I-26 Southbound TransModeler Analysis Tables Page 1) Intersection & Freeway Segment Level of Service (LOS) Characteristics ........................ 3 2) 2011 Base Year No-Build Freeway Operations Summary ............................................... 8 3) 2011 Base Year Build – 8/6 Lane Combination Alternative Freeway Ops Summary ....... 9 4) 2011 AM & (PM) Peak Hour Intersection Capacity Analysis Results Summary ............. 11 5) 2040 Design Year No-Build Alternative - Freeway Operations Summary ...................... 15 6) 2040 Design Year Build – 8/6 Lane Combination Alternative Freeway Ops Summary .. 16 7) 2040 AM & (PM) Peak Hour Intersection Capacity Analysis Results Summary ............. 18 8) Failure Year Analysis – I-26 Freeway Operations Summary ......................................... 21 9) Model Calibration Summary .......................................................................................... 25 10) 2011 Base Year Interchange System MOE Results ...................................................... 27 11) 2011 Base Year US 25 Corridor MOE Results .............................................................. 27 12) 2011 Base Year Interchange Ramp Terminal MOE Results .......................................... 28 13) 2040 Design Year Interchange System MOE Results ................................................... 29 October 2014 ii