Freeway Weaving and Ramp Junction Analysis

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1 TEXAS TECH UNIVERSITY Freeway Weaving and Ramp Junction Analysis Along IH 27 at Plainview, TX Hao Xu, Jared A. Squyres, Wesley Kumfer, and Hongchao Liu 7/15/2011

2 Table of Contents Project Description... 2 Data... 2 Methodology and Approach... 2 Study Results... 8 Summary Reference

3 Project Description As part of the Plainview IH 27 project involving the conversion of two way frontage roads into one way frontage roads, TxDOT will be adding additional ramps to facilitate movement on and off the main lanes of IH 27. As part of the Interstate Justification reporting requirements, a level of service/weaving analysis is required to determine the impacts to the free flow of traffic along the main lanes. This project models the traffic flow and conducts weaving and ramp junction analysis along the main lanes of I 27 between FM 3466 to SH 194. In this study, the interchange of IH 27 and U.S. Hwy 70 was also simulated to analyze the effect of the proposed one way frontage road and interchange configuration compared to existing ones with three groups of traffic volumes: existing, projected 2015, and projected Data The data used in the study was provided by TxDOT and supplemented by data collected during site visits to the interchange. Traffic counts (volumes, speeds, and classes) with 15 minute intervals along main lanes of the studied IH 27 segment were collected for this project, and traffic volumes and signal timing plans at IH 27 and U.S. Hwy 70 were reused from an earlier task of the Plainview I 27 project [1]. Projected daily traffic volumes for 2015 and 2035 were provided by TxDOT, along with the preliminary geometric schematic plan view. Methodology and Approach Weaving is defined as the crossing of two or more traffic streams traveling in the same general direction along a significant length of highway without the aid of traffic control devices (with the exception of guide signs). When an on ramp is closely followed by an off ramp and the two are joined by an auxiliary lane, they form a weaving segment. If a one lane on ramp is closely followed by a one lane off ramp and the two are not connected by an auxiliary lane, the merge and diverge movements are considered separately using procedures for the analysis of ramp junctions [2]. Impacts of the proposed and existing ramps to the traffic along the main lanes are caused by weaving, merging, and diverging movements at junctions of the freeway and ramps. Therefore, this study analyzed each junction by using a weaving or ramp junction analysis procedure as necessary. The proposed on ramp, the existing off ramp, and the proposed auxiliary lane along IH 27 northbound between FM 3466 and US 70 comprise a weaving segment. The other ramps (one proposed on ramp, two existing on ramps, two proposed off ramps, and two existing off ramps) in the studied segment were analyzed as isolated ramp junctions. The tool used to analyze the weaving segment and ramp junctions in this project was HCS HCS 2000 implements the procedures defined in the Highway Capacity Manual 2000 (HCM 2

4 2000), including commonly used analysis methods for freeway weaving segments and ramp junctions [2]. The methodological process used to construct the weaving and ramp junction analysis was performed in the following steps: 1. The traffic volume data along IH 27 collected by TxDOT for this project were processed. The peak 15 minute traffic volume, the peak hour volume, and the Peak Hour Factor () at each traffic count location were calculated. Peak hour and peak 15 minute times at each traffic count location are different from times at other traffic count locations, so peak hour and peak 15 minute volumes were used without considering the times. The processed data is shown in Table 1 and the peak hour volumes are also shown in Figure 1 Figure The projected peak hour volumes for 2015 and 2035 were calculated by multiplying projected daily volumes by 10%, as indicated by various references. 3. The required input data were collected, and values at the studied weaving segment and isolated ramp junctions for 2011, 2015, and 2035 were estimated separately, as shown in Table 2, Table 3 and Table 4. The required data and values were input into HCS 2000 to generate analysis results. The IH 27 and US 70 interchange was modeled and simulated using Synchro and SimTraffic. The Synchro models for the existing two way frontage roads and interchange configurations were reused from the former task of the Plainview IH 27 project [1]. Models for the proposed frontage roads and interchange configuration were developed in this study. Current traffic volumes, projected 2015 traffic volumes, and projected 2035 traffic volumes at this interchange were applied to the two configurations: the existing one and the proposed one. Simulation results were generated by SimTraffic and delay values were compared to illustrate the effect of the proposed configuration. 3

5 Table 1: PROCESSED TRAFFIC DATA OF MAIN LANES PEAK 15 MINUTE PEAK 15 MINUTE PEAK HOUR PEAK HOUR MAIN LANE PEAK MAIN LANE PEAK LOCATION MAIN LANE RAW FILE NAME TIME TIME 15 MINUTE HOUR IH 27 NB DL MP :30 PM 90 6:15 PM A 1538V rdf' IH 27 NB PL MP :30 AM 46 9:00 AM A 1541V rdf' IH 27 NB DL MP :30 PM 94 5:30 PM 329 '0164A 1540V rdf' IH 27 NB PL MP :45 AM 46 9:00 AM 78 '0164A 1147V rdf' IH 27 NB DL MP :45 PM 63 3:30 PM 218 '0164A 1151V rdf' IH 27 NB PL MP :45 AM 22 4:15 PM 47 '0164A 1537V rdf' IH 27 NB DL MP :00 PM 83 3:00 PM 317 '0164A 1151V rdf' IH 27 NB PL MP :00 AM 41 9:00 AM 86 '0164A 1149V rdf' IH 27 NB DL MP :45 PM 98 3:30 PM 328 '0164A 1119V rdf' IH 27 NB PL MP :00 AM 42 9:00 AM 76 '0164A 1145V rdf' IH 27 NB DL MP :45 PM 76 3:00 PM A 1119V rdf' IH 27 NB PL MP :00 AM 35 2:30 PM 67 '0164A 1536V rdf' IH 27 SB DL MP :45 PM 91 3:30 PM A 1536V rdf' IH 27 SB PL MP :45 PM 54 3:45 PM 106 '0164A 1151V rdf' IH 27 SB DL MP :45 PM 91 3:30 PM 304 '0164A 1117V rdf' IH 27 SB PL MP :00 AM 39 1:30 PM 95 '0164A 1145V rdf' IH 27 SB DL MP :45 PM 89 3:00 PM 298 '0164A 1541V rdf' IH 27 SB PL MP :45 PM 37 1:30 PM 95 '0164A 1144V rdf' IH 27 SB DL MP :45 PM 84 3:30 PM 289 '0164A 1119V rdf' IH 27 SB PL MP :45 PM 39 4:00 PM 118 '0164A 1540V rdf' IH 27 SB DL MP :45 PM 54 3:30 PM 198 '0164A 1537V rdf' IH 27 SB PL MP :00 PM 35 4:15 PM 92 '0164A 1539V rdf' IH 27 SB DL MP :45 PM 91 3:00 PM A 1149V rdf' IH 27 SB PL MP :30 PM 40 4:15 PM 105 '0164A 1538V rdf' IH 27 SB DL MP :00 PM 81 12:45 PM 287 '0164A 1118V rdf' IH 27 SB PL MP :30 PM 34 4:15 PM 107 '0164A 1147V rdf' 4

6 Figure 1 ESTIMATED PEAK HOUR IN MAIN LANES AND RAMPS 2011 (1) Figure 2 ESTIMATED PEAK HOUR IN MAIN LANES AND RAMPS 2011 (2) 5

7 Figure 3 ESTIMATED PEAK HOUR IN MAIN LANES AND RAMPS 2011 (3) Table 2: REQUIRED INPUT DATA AND VALUES FOR THE WEAVING SECTION AND RAMP JUNCTIONS (2011) DIRECTION/SEGMENT RAMP TYPE RAMP NUMBER IN THE PLAN VIEW LANES RAMP LENGTH OF ACCELERATION LANES /DECELERATION LANE FFS RAMP FFS RAMP LENGTH OF ANALYSIS PERIOD RAMP RAMP PERCENTAGE PERCENTAGE OF HEAVY VEHICLES OF HEAVY VEHICLES NB/NORTH OF US70 EXISTING ON RAMP FT 70 MPH 35 MPH 303 VPH 101 VPH 1 HOUR % 8% NB/BETWEEN 24TH ST AND SH194 EXISTING OFF RAMP FT 70 MPH 35 MPH 404 VPH 49 VPH 1 HOUR % 8% SB/BETWEEN 24TH ST AND SH194 EXISTING ON RAMP FT 70 MPH 35 MPH 463 VPH 80 VPH 1 HOUR % 8% SB/SOUTH OF 24TH STREET PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 543 VPH 40 VPH 1 HOUR % 8% SB/NORTH OF US70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 503 VPH 59 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 444 VPH 20 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED ON RAMP RAMP FT 70 MPH 35 MPH 424 VPH 80 VPH 1 HOUR % 8% REQUIRED INPUT DATA AND VALUES FOR WEAVING ANALYSIS 2011 DIRECTION/SEGMENT RAMP NUMBER IN NUMBER LENGTH OF WEAVING TYPE THE PLAN VIEW OF LANES WEAVING SEGMENT LENGTH FFS TERRAIN ANALYSIS PERIOD A C B D NB/BETWEEN FM3466 AND US 70 TYPE A RAMP 1 & RAMP FEET 70 MPH LEVEL 1 HOUR 265 VPH 0 VPH 142 VPH 38 VPH A C B D A C B D 6

8 Table 3: REQUIRED INPUT DATA AND VALUES FOR THE WEAVING SECTION AND RAMP JUNCTIONS (2015) DIRECTION/SEGMENT RAMP TYPE RAMP NUMBER IN THE PLAN VIEW LANES REQUIRED INPUT DATA AND VALUES FOR RAMP JUNCTION ANALYSIS 2015 RAMP LENGTH OF ACCELERATION LANES /DECELERATION LANE FFS Table 4: REQUIRED INPUT DATA AND VALUES FOR THE WEAVING SECTION AND RAMP JUNCTIONS (2035) RAMP FFS RAMP LENGTH OF ANALYSIS PERIOD RAMP RAMP PERCENTAGE PERCENTAGE OF HEAVY VEHICLES OF HEAVY VEHICLES NB/NORTH OF US70 EXISTING ON RAMP FT 70 MPH 35 MPH 360 VPH 200 VPH 1 HOUR % 8% NB/BETWEEN 24TH ST AND SH194 EXISTING OFF RAMP FT 70 MPH 35 MPH 560 VPH 220 VPH 1 HOUR % 8% SB/BETWEEN 24TH ST AND SH194 EXISTING ON RAMP FT 70 MPH 35 MPH 240 VPH 270 VPH 1 HOUR % 8% SB/SOUTH OF 24TH STREET PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 510 VPH 130 VPH 1 HOUR % 8% SB/NORTH OF US70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 380 VPH 120 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 260 VPH 40 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED ON RAMP RAMP FT 70 MPH 35 MPH 320 VPH 270 VPH 1 HOUR % 8% REQUIRED INPUT DATA AND VALUES FOR WEAVING ANALYSIS 2015 DIRECTION/SEGMENT RAMP NUMBER IN NUMBER LENGTH OF WEAVING TYPE THE PLAN VIEW OF LANES WEAVING SEGMENT LENGTH FFS TERRAIN ANALYSIS PERIOD A C B D NB/BETWEEN FM3466 AND US 70 TYPE A RAMP 1 & RAMP FEET 70 MPH LEVEL 1 HOUR 240 VPH 0 VPH 250 VPH 120 VPH A C B D A C B D DIRECTION/SEGMENT RAMP TYPE RAMP NUMBER IN THE PLAN VIEW LANES REQUIRED INPUT DATA AND VALUES FOR RAMP JUNCTION ANALYSIS 2035 RAMP LENGTH OF ACCELERATION LANES /DECELERATION LANE FFS RAMP FFS RAMP LENGTH OF ANALYSIS PERIOD RAMP RAMP PERCENTAGE PERCENTAGE OF HEAVY VEHICLES OF HEAVY VEHICLES NB/NORTH OF US70 EXISTING ON RAMP FT 70 MPH 35 MPH 500 VPH 280 VPH 1 HOUR % 8% NB/BETWEEN 24TH ST AND SH194 EXISTING OFF RAMP FT 70 MPH 35 MPH 780 VPH 310 VPH 1 HOUR % 8% SB/BETWEEN 24TH ST AND SH194 EXISTING ON RAMP FT 70 MPH 35 MPH 330 VPH 380 VPH 1 HOUR % 8% SB/SOUTH OF 24TH STREET PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 710 VPH 180 VPH 1 HOUR % 8% SB/NORTH OF US70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 530 VPH 160 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED OFF RAMP RAMP FT 70 MPH 35 MPH 370 VPH 50 VPH 1 HOUR % 8% SB/BETWEEN FM3466 AND US 70 PROPOSED ON RAMP RAMP FT 70 MPH 35 MPH 350 VPH 380 VPH 1 HOUR % 8% REQUIRED INPUT DATA AND VALUES FOR WEAVING ANALYSIS 2035 DIRECTION/SEGMENT RAMP NUMBER IN NUMBER LENGTH OF WEAVING TYPE THE PLAN VIEW OF LANES WEAVING SEGMENT LENGTH FFS TERRAIN ANALYSIS PERIOD A C B D NB/BETWEEN FM3466 AND US 70 TYPE A RAMP 1 & RAMP FEET 70 MPH LEVEL 1 HOUR 350 VPH 0 VPH 340 VPH 150 VPH A C B D A C B D 7

9 Study Results The weaving segment of IH 27 northbound between FM 3466 and US 70 was analyzed by using the weaving analysis tool in HCS The results are shown in Table 5. As shown in the table, speed is likely to decrease as density through this area increases. Table 5: ANALYSIS RESULTS FOR THE WEAVING SEGMENT YEAR 2011 YEAR 2015 YEAR 2035 WEAVING SEGMENT SPEED (mi/h) WEAVING SPEED (mi/h) NON WEAVING SPEED (mi/h) WEAVING SEGMENT DENSITY (pc/mi/ln) LEVEL OF SERVICE, LOS A A A CAPACITY AS A 15 MINUTE FLOW RATE (veh/h) CAPACITY AS A FULL HOUR (veh/h) Terminology included in this table includes: WEAVING SEGMENT SPEED: space mean speed of all vehicles in the weaving segment WEAVING SPEED: space mean speed of weaving vehicles in the weaving segment NON WEAVING SPEED: space mean speed of non weaving vehicles in the weaving segment LEVEL OF SERVICE: Levels of service in weaving segments are defined in terms of density for all cases of stable operation. The LOS criteria was is in Table 6 CAPACITY AS A 15 MINUTE FLOW RATE: capacity under prevailing conditions stated as a flow rate for the peak 15 min of the hour CAPACITY AS A FULL HOUR : capacity under prevailing conditions expressed as an hourly volume Table 6: LOS CRITERIA FOR WEAVING SEGMENTS LEVEL OF SERVICE, LOS A B C D E F WEAVING SEGMENT DENSITY (pc/mil/ln) <= >27.0 Isolated ramp junctions were analyzed by using the ramp analysis tool in HCS Analysis results are shown in Table 7: 8

10 Table 7: ANALYSIS RESULTS FOR RAMP JUNCTIONS RAMP DESCRIPTION NB/NORTH OF US70 NB/BETWEEN 24TH ST AND SH194 SB/BETWEEN 24TH ST AND SH194 SB/SOUTH OF 24TH STREET SB/NORTH OF US70 SB/BETWEEN FM3466 AND US 70 SB/BETWEEN FM3466 AND US 70 DENSITY IN THE MERGING INFLUENCE AREA (pc/mil/ln) LEVEL OF SERVICE, LOS A A A A A A A SPACE MEAN SPEED OF VEHICLES WITHIN RAMP INFLUENCE AREA (mil/h) YEAR 2015 RAMP DESCRIPTION NB/NORTH OF US70 NB/BETWEEN 24TH ST AND SH194 SB/BETWEEN 24TH ST AND SH194 SB/SOUTH OF 24TH STREET SB/NORTH OF US70 SB/BETWEEN FM3466 AND US 70 SB/BETWEEN FM3466 AND US 70 DENSITY IN THE MERGING INFLUENCE AREA (pc/mil/ln) LEVEL OF SERVICE, LOS A A A A A A A SPACE MEAN SPEED OF VEHICLES WITHIN RAMP INFLUENCE AREA (mil/h) YEAR 2035 RAMP DESCRIPTION NB/NORTH OF US70 NB/BETWEEN 24TH ST AND SH194 SB/BETWEEN 24TH ST AND SH194 SB/SOUTH OF 24TH STREET SB/NORTH OF US70 SB/BETWEEN FM3466 AND US 70 SB/BETWEEN FM3466 AND US 70 DENSITY IN THE MERGING INFLUENCE AREA (pc/mil/ln) LEVEL OF SERVICE, LOS A A A A A A A SPACE MEAN SPEED OF VEHICLES WITHIN RAMP INFLUENCE AREA (mil/h) YEAR

11 Delay values simulated for the IH 27 and US 70 interchange are shown in Table 8. A comparison of simulation results for the two configurations, the existing one and the proposed one, is shown in Table 9. Table 8: DELAY VALUES SIMULATED FOR IH 27 AND US 70 Movements / (Delay/veh (s)) ID # ConfigDate Scenario EBL EBT EBR WBL WBT WBR NBL NBT NBR SBL SBT SBR AM Noon PM AM Noon PM AM Noon PM AM Noon PM AM Noon PM AM Noon PM AM Noon PM AM Noon PM West Intersection (US 70 and I 27) 6 East Intersection (US 70 and I 27) Current Future Current Future

12 Table 9: RESULTS COMPARISON FOR THE EXISTING AND THE PROPOSED INTERCHANGE CONFIGURATION (Future Delay Current Delay) Movements / (Delay/veh (s)) ID # Date Scenario EBL EBT EBR WBL WBT WBR NBL NBT NBR SBL SBT SBR AM Noon PM AM Noon PM AM Noon PM AM Noon PM West 6 East Summary The weaving and ramp junction analyses presented in this report illustrate that the proposed additional ramps in the study area have a slight impact on the free flow of traffic along the main lanes. The Level of service in each ramp junction (or weaving segment) influence area is Level A, even with the highest projected 2035 traffic volume. Vehicle speeds in the influence areas will be a little bit lower than the free flow speeds, but this will not affect the fluidity of the traffic flow in the main lanes. Simulation results of the IH 27 and US 70 interchange showed that the new frontage road and interchange configurations will greatly reduce delay at the interchange, which is often congested severely because of the business area on the northwest of the interchange. Therefore, the research team recommends that these new configurations be adopted to improve traffic conditions on IH 27. Reference 1. Hongchao Liu, Hao Xu, and Rhett Dollins, Congestion Mitigation at IH 27 and U.S. Hwy 70 in Plainview, TX. Lubbock, TX. April, Transportation Research Board, Highway Capacity Manual TRB. Washington, D.C.,

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