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serl/ing yOll with pride Memorandum Montana Department of Transportation PO Box 201001 Helena, MT 59620-1001 To: Dwane Kailey, P.E. District Administrator Missoula From:gw Danielle C. Bolan, P.E. Traffic Engineer Date: Subject: February 5,2007 Missoula Reserve Street and Mullan Road Northbound Dual Left-Tum Study The purpose of this study is to determine whether a northbound dual left-tum at the intersection of Mullan Road and Reserve Street in Missoula would improve operations at this intersection. A request came from the Missoula District to study the intersection to determine if this is a feasible option for this location. Traffic volumes, capacity analyses, crashes, and existing geometries were used in the completion of this study. In conclusion, a northbound dual left-tum lane at this intersection would improve operations and the recommended design is attached to this document. TraffIc Volumes Traffic data was collected on May 9th, 2006. Turning movements were taken at the intersection of Mullan Road & Reserve Street and at the intersection of Mullan Road & Clark Fork Lane. An origin-destination study was completed for the northbound, left-turning vehicles on Reserve Street. Turning movements for the AM, Noon, and PM peaks for both intersections are displayed in Figure 1. Figure 1 HP. PEPIO[' PE F' 10D I-mm L V1 Mullan Rood ---PAGE BREAK--- HR. RE R100 . HR. PER 100 _ PERIOD Mullan Roo(j Mullan Rood The origin and destination study showed what percentage of northbound, left-turning vehicles off of Reserve Street turned into Wal-Mart or continued westbound on Mullan Road. This helped determine the lane utilization for the proposed dual left tum on Reserve. Figure 2 shows the break down of the origin destination study. Figure 2 66% 42% 67% 34% 58% 33% MUllan Rood Mullan Rood Mullan Rood 2 L V1 > L lfJ et: ---PAGE BREAK--- Crashes A crash analysis was completed for the intersection and there were 130 reported crashes from 01/01/2003 to 12/31/2005. The crash breakdown is listed below in Figure 3. Figure 3 # of Crashes Rear-End 89 NB Left-Turn Opposite Direction 21 SB Left-Turn Opposite Direction 4 Side-Swipe Same Direction 6 Side-Swipe Opposite Direction 2 Right Angle 6 Single Vehicle 2 Pedestrian 2 A more in-depth review of the accident trends in this intersection was completed previously with the report on the State Farm Insurance Intersections. The conclusion of that study was to change the permissive/protected left turns to a protected only movement. Geometries Design provided by the district The geometries proposed by the district were reviewed. Several issues were identified with the proposed design. Right turning truck movements (WB-67) were of concern. Westbound right turning trucks can make the movement unimpeded. Southbound and eastbound right turning trucks can make the movement if the truck uses both through lanes. Northbound trucks turning right onto Mullan Road cannot make the movement without off tracking onto the curb and sidewalk (see attachment This is due to the fact that the WB lanes were shifted to the south and reduced the lane width available for right tUTI1ing vehicles. Also, this movement was originally designed for a WB-62. Also, a westbound WB-67 cannot tum left from the outside left tum lane without encroaching on the vehicle in the inside left tum lane. This movement is of concern. (See Attachment 1) A northbound WB-67 turning left cannot make the tum from the inside lane without encroaching on the eastbound left tum lane. In order to accommodate this movement the stop bar would have to be moved back 65 feet. It would be desirable for the design to accommodate this movement since the inside left tum lane will serve Wal-Mart. If a truck going to Wal-Mart has to make the left tum from the outside lane, it will have to weave back into the inside lane in the short distance between Reserve Street and Clark Fork Lane. (See Attachment 1) Proposed Design After reviewing the design provided by the district, we evaluated a proposed design that would address the identified concerns. The proposed design is attached to this document. 3 ---PAGE BREAK--- The lane configuration for the east approach did not change fron1 existing conditions. With the existing configuration, the largest truck that can accommodated for the northbound right turning movements is a WB-65. This condition will not change with the proposed modifications. Westbound, WB-67 trucks turning left from the outside lane will be able to make the movement simultaneously with a passenger vehicle without encroaching into the inside northbound left tum lane. (See Attachments 2 and 3) The island in the northwest quadrant would be eliminated to allow room for northbound left turning trucks. By removing the island, a WB-67 truck would not encroach into the eastbound left tur11 lane. A northbound WB-67 turning left from the inside left lane and a WB-67 truck turning left from the outside left lane can make their movements' simultaneously. (See Attachment 3) With the removal of the island in the northwest quadrant, the comer radii will need to be redesigned in order to better define the right turning movement for the southbound direction. The constraint used in redesigning the comer was the allowance of a southbound right turning WB-67 to encroach into both of the through lanes on the west approach. Two new ADA ramps will need to be constructed. (See Attachment 2) Removing the northwest island and redesigning the northwest comer caused the crosswalks for the east and north approaches to be lengthened. The crosswalk for the east approach was lengthened from 80.2 ft (from southwest comer to island) to 101 ft. The crosswalk for the north approach was lengthened from 78.8 ft (from northeast comer to island) to 102.3 ft. (See Attachment 4) Removing the island in the northwest quadrant will require significant signal modifications. New conduit will need to be bored under Reserve Street from the NE quadrant to the NW quadrant. The modifications will require a new signal pole and mast arm in the NW quadrant. Depending on the actual signal design, a near sighted signal may need to be provided for the WB direction. The lane configuration changes on the west approach will require the removal of the raised median between Reserve St. and Clark Fork Lane. Depending on the actual design on Reserve St., the raised median on the south approach may need to be modified. Pavement markings and signs will need to be revised on the west, south, and north approaches. An overhead lane configuration sign should be installed for the NB direction on the south approach for the dual left tum lanes. The bicycle lanes on the west and south approaches will need to be ren10ved. There will need to be a discussion with the local government on the removal of these bicycle lanes to accommodate the dual left turn. Discussion will also need to take place on how the removal of the bicycle lanes affects the overall continuity of the bicycle lane. Capacity Analysis Existing Conditions A capacity analysis was completed for the existing conditions and the proposed northbound dual left-tum lane. The existing timing is an 8-phase operation with a leading left phase for northbound and southbound vehicles and a lead-lag phase for eastbound and westbound vehicles. The existing times implemented in the controller were used in this analysis. The phase diagram for the existing timing is shown in Figure 4. 4 ---PAGE BREAK--- Figure 4 - Phase Diagram - Existing Conditions 05 05 03 04 The cycle length is 115 seconds during the morning and changes to 175 seconds during the afternoon and evening. The intersection is semi-actuated with actuation on Mullan and in the left tum lanes on Reserve. The existing capacity analysis of the intersection is shown in Figure 5. Delay is measured in seconds. Figure 5 - Capacity Analysis - Existing Conditions AM Peak Noon Peak PM Peak LOS D LOS - D LOS-E Delay - 37.7 Delay - 50.5 Delay - 65.5 LOS - C LOS-D LOS - D LOS - E LOS-D LOS - E LOS - E LOS-E LOS - F Delay - 31.5 Delay- 38.9 Delay - 48.3 Delay - 65.9 Delay - 49.6 Delay - 64.3 Delay - 63.2 Delay - 69.0 Delay - 116.0 LOS-D LOS - C LOS - D Delay 41.5 Delay - 34.1 Delay - 43.8 It was brought to our attention that the intersection behaves as though it is pre-timed. The only actuation that was occurring was on Reserve Street. Mullan Road was operating as pre-timed, which unnecessarily backs up traffic on Reserve Street during off-peak hours. The intersection was observed at 9:30 PM and it does behave like a pre-timed signal. Traffic was queued on Reserve Street for a significant portion ofthe cycle. It was discovered that the video detection for Mullan Road is no longer operating properly and must be replaced. Due to high traffic volumes, this problem did not affect the performance of the intersection during peak hours as all phases of the cycle maxed out nearly every time. Proposed Conditions The intersection was analyzed under a number of different scenarios. Various cycle (120, 150, and 180 seconds) were explored. With Reserve Street being mainline, 60% of the cycle length was allotted for Reserve and the remaining 40% of the cycle length was given to Mullan Road for all proposed scenarios. Also, significant discussion has taken place to change the existing 8-phase operation (as shown in Figure 3) due to the high number of crashes involving the NB and SB left turning vehicles. Therefore, the existing 8-phase operation was not optimized. After examining the various signal timings, it was determined that the morning operated most effectively with a 120 second cycle length for each different scenario. While the afternoon and 5 ---PAGE BREAK--- evening peaks also operated most effectively at 120 second cycle it was determined to continue with the 180 second cycle length for these peaks due to the traffic volumes, speed along Reserve Street, and the coordination of the Reserve Street corridor. Existing Geometry wi Modified Phase Operation The intersection was analyzed with the modified phase operation and the existing geometry. The modified 8-phase operation changes the left turns from protected/pennissive to protected only and is shown in Figure 6. The optimized capacity analysis of this scenario is displayed in Figure 7. Figure 6 - Modified Phase Diagram for Existing Geometry Figure 7 - Existing Geometry wi Modified Phase Operation Performance AM Peak Noon Peak (120 Sees.) (180 Sees.) LOS - D LOS - D Delay - 42.9 Delay - 52.7 LOS - C LOS-D LOS - D LOS -E LOS-D LOS - E Delay - 33.6 Delay - 34.8 Delay - 48.2 Delay - 70.2 Delay - 53.4 Delay - 68.2 I LOS - C I I LOS - 0 I Delay - 29.5 Delay - 38.6 Proposed Design wi Modified Phase Operation LOS - E Delay - 77.2 PM Peak (180 Sees.) LOS - D Delay - 67.6 LOS-E ID~:-s~.61 Delay 52.8 LOS - F Delay - 77.6 In order for the dual northbound left turn lanes to operate safely, the 8-phase operation was Inodified to a lead-lag cycle for northbound and southbound movements. The modified 8-phase operation for the proposed design is shown in Figure 8. The optimized capacity analysis of the intersection is shown in Figure 9. 6 ---PAGE BREAK--- Figure 8 - Modified Phase Diagram - Proposed Design Figure 9 - Capacity Analysis - Proposed Design i DelaY-38.2 D:~~~3~'7IDelaY_48'2 Delay - 30.4 Delay-66.3 Delay-50.2 re1a -71.9 ~ LOS-D I Delay - 36.5 LOS - E PM Peak (180 Sees.) L ~ D~::-4:0L LOS - E LOS - E LOS - F DelaY -76_S 1 lela -81.6 Delay - 46.4 Noon Peak (180 Sees.) LOS - D Delay - 43.2 LOS -D LOS - E LOS - D AM Peak (120 Sees.) LOS-D Delay - 30.2 LOS-D LOS - D It was noted that the pedestrian clearance interval for the pedestrians accessing the northwest quadrant would need to be lengthened. Currently, the clearance interval is 25 seconds. The interval would need to be lengthened to 30 seconds with this design. The clearance interval would take time away from phase 1 (left turning westbound vehicles). However, pedestrian volumes for all approaches were low during data collection and should not consistently impede operations. Conclusions The intersection of Reserve Street and Mullan Road is currently operating at capacity. There are safety concerns at this intersection with the permissive left turns from Reserve Street. To address the safety concerns with the left turns, a protected only left tum phase for the NB and SB directions will need to be implemented. By changing the signal phasing to allow only protected left turns will add to the delay at this intersection during off peak times. Since the majority of the left turns can not make permissive movelnents during the peak hours, the operation during the peak hours will not change significantly. The delay during the off-peak hours can be reduced if the intersection is operated as fully actuated. Due to the geometries on Reserve Street, the NB left tum can not be lengthened without widening the bridge to the south. One way to improve the operations for theNB approach is to use the width available at this intersection and provide a dual left tum lane on the south approach. Currently the left tum movements back up into the inside through lane. By providing a dual left tum lane the available storage for this movement can be increased. By providing two lanes for the NB left tum movement the time required to serve this movement can be decreased. The time gained from the additional NB lane can be redistributed to all the other movements within the intersection. This allows the intersection to operate at a better level of service than the current operations. 7 ---PAGE BREAK--- To accommodate a NB dual left tum lane the island in the northwest quadrant will need to be removed and will require modifications to the traffic signal. Crosswalk will be increased on the west and north approaches, and the bicycle lanes on the west and south approaches will be removed. The raised median on Mullan Road between Reserve St. and Clark Fork Lane will need to be removed and the pavement markings on the west, south, and north approaches will have to be modified. In addition to minor signing modifications, a overhead lane use control sign structure should be installed on the south approach. The corner radii and ADA ramps in the NW quadrant will need to be modified. With these modifications, a dual NB left turn can be provided at this intersection. Recommendation We recommend that the proposed design be implemented to provide for dual NB left tum lanes at the Mullan and Reserve St. intersection. If you have any questions, please call R. 1. Snyder at 444-1272. Cc. ~'ra:r:[e Stack District Project Engineer Missoula Duane Williams - Traffic and Safety Engineer Danielle Bolan Traffic Engineer Glen Cameron District Traffic Engineer - Missoula Phil Balsey, P.E. - Electrical Section Bob Johnson Geometries Section RJ. Snyder - Traffic Section Preconstruction File 8