Reference number /VP. Lafayette Downtown Congestion Study - Additional Traffic Analysis

Transcription

1 To James Hinkamp and Tony Coe, City of Lafayette Date January 19, 2017 Copies Reference number /VP From Michael Iswalt and Vanessa Peers File reference 4-05 Subject Lafayette Downtown Congestion Study - Additional Traffic Analysis This memorandum summarizes additional traffic analyses to support the Short List of strategies for the Downtown Congestion Study. At the request of the Steering Committee, three strategies were analyzed in further detail: 1) School Street One-Way Westbound, 2) Other design options for the Mount Diablo Road Diet, and 3) an Alternative School Stagger Start Time option. 1 School Street One-Way Westbound The School Street One-Way Westbound strategy would convert School Street to one-way westbound from First Street to Moraga Road. There is enough road space to provide a left and right-turn lane, additional on-street parking, and can accommodate the recommended pedestrian and bicycle facilities (a buffered shared pedestrian and bicycle lane) proposed as part of the School Street Complete Street strategy. Figure 1 presents the proposed design. Figure 1: School Street One-Way Westbound Converting School Street to one-way westbound only would prohibit the existing left-turn from Moraga Road to School Street. This would divert vehicles from Moraga Road to either St. Mary s Road and Avalon Avenue (for vehicles traveling to/from the south) or Moraga Boulevard and School Street (for vehicles traveling to/from the north). Figure 2 illustrates these diversions from Moraga Road with the School Street One-Way Westbound strategy. Page 1 of 9

2 Figure 2: School Street One-Way Westbound Diversion The pros for this strategy include: Eliminates the southbound left-turn from Moraga Road, which eliminates the situation where vehicles waiting to make the left-turn block the southbound through travel lane. Removes a signal phase and simplifies the signal operation. Diverts approximately 100 trips (80 from the north and 20 from the south) during the morning school peak hour and 50 trips during the afternoon peak hour from Moraga Road. These are volumes that currently make the southbound left-turn or northbound right-turn from Moraga Road to School Street to travel eastbound on School Street. The 80 vehicles diverted from the north would need to use Moraga Boulevard and 1 st Street, while the 20 vehicles from the south would need to use St. Mary s Road and Avalon Avenue to reach School Street. The cons for this strategy include: Page 2 of 9

3 The diversion of traffic would impact residential neighborhoods. The City s General Plan has a policy to limit cut-through traffic of this kind in neighborhoods. However, the volumes are relatively small. We do not have counts on 1 st Street or Avalon Avenue, but field observations indicate that there a capacity issue does not currently exist. It is unlikely that this diversion would result in a local intersection impact. However, increased traffic could lead to safety and quality of life impacts on these residential streets. The conversion to one-way westbound could limit access to a few businesses on the south side of School Street between Moraga Road and 1 st Street. This strategy could be implemented relatively quickly as it does not require any significant street reconstruction. It could also be built prior to the Brook-School connection, which could take time to implement. After the Brook-School connection is built, School Street would be returned to two-way traffic operations. To accommodate the extra left turns at Moraga Boulevard, the southbound left-turn pocket recommended in the Short List is essential for this strategy to succeed. The additional traffic on St. Mary s Road and Avalon Avenue is negligible. These changes were coded into the VISSIM microsimulation model that was developed for the mid-day (MD)/PM peak period to assess the feasibility of this strategy. The model analyzed traffic operations under future year 2025 conditions, which assumes a 10% increase in traffic across the study area. The intersection level-of-service (LOS) and the travel time results are provided in Table 1. Table 1: School Street One-Way Westbound Capacity Analysis Results Intersection 2025 Baseline 2025 School Street WB only Delay LOS Delay LOS Mt Diablo Blvd /Oak Hill Rd 26 C 28 C Mt Diablo Blvd / Moraga Rd 49 D 49 D Moraga Rd / Moraga Blvd 49 D 45 D Moraga Rd / School St / Brook St 94 F 68 E Moraga Rd / St Mary s Rd 60 E 42 D Mt Diablo Blvd / 1 st St 31 C 29 C Travel time Moraga Road NB 04:27 04:25 Moraga Road SB 03:12 02:10 Average delay per vehicle 02:17 02:03 Compared to the 2025 Baseline (no changes to the roadway), the School Street One-Way Westbound strategy combined with the southbound left-turn lane at Moraga Boulevard provides an overall improvement in traffic performance along Moraga Road. However, Moraga Road/School Street/Brook Street would still operate at LOS E during the 2025 PM peak hour scenario. Page 3 of 9

4 This concept does significantly reduce the delay at the southbound (from 59 seconds to 22 seconds) and westbound (from 210 seconds to 160 seconds) approaches at the Moraga Road/School Street/Brook Street intersection. Operations at the north and eastbound approaches improve slightly, although not as much as the other approaches. The reduced delays at the southbound approach are a result of better utilization of both southbound travel lanes with the elimination of left turning vehicles blocking the southbound travel lane. Additional queuing space at the westbound approach and the removal of the southbound protected left-turn phase (left-turn arrow) also contributes to the overall improvement in performance. Southbound travel times would improve significantly due to the removal of the left-turns at School Street, while northbound travel times would remain mostly unchanged. The School Street One-Way Westbound concept is a viable short-term strategy before the full Brook- School Connection is implemented. 2 Alternative Mount Diablo Blvd Road Diet Concept Arup has developed an alternative conceptual design for the Mount Diablo Boulevard road diet strategy between Acalanes Road and Risa Road. Currently, this segment of Mount Diablo Boulevard has two lanes in each direction, limited medians, center left-turn lanes at key intersections, a sidewalk on the south side, 2-3 ft shoulders, with the shoulder on the north side of the street striped as a bike lane. Figure 3 shows Mount Diablo Boulevard facing west towards the Lafayette Reservoir entrance. Figure 3: Mount Diablo Blvd - facing west towards the Lafayette Reservoir Entrance Page 4 of 9

5 The original road diet concept along Mount Diablo Boulevard, which would convert the existing street cross-section from two lanes in each direction to one lane in each direction with a continuous median, left-turn lanes, wide buffered bike lanes on both sides, and a new sidewalk on the north side. Figure 4 presents a segment of this design just west of Risa Road and Figure 5 presents a cross-section. The traffic analysis presented in the August 26 th, 2016 memo indicated that this original road diet concept would provide sufficient capacity under typical operating conditions with future year 2040 traffic volumes. The alternative road diet concept has more capacity because of the second westbound travel lane. Therefore, the traffic operations for the alternative concept should exceed the performance reported in the August 26 th, 2016 memo. Figure 4: Original Proposed Road Diet West of Risa Road The Steering Committee raised concerns that removing one travel lane in each direction could create an issue during an emergency evacuation. To address these concerns, the concept was redesigned to accommodate two westbound travel lanes and one eastbound travel lane. Figure 6 presents the crosssection for the modified concept. Page 5 of 9

6 Figure 5: Original Proposed Road Diet Cross-Section Figure 6: Modified Road Diet Cross-Section Figure 7 presents two of the segments from El Nido Ranch Road to Risa Road. Page 6 of 9

7 Modified Road Diet Concept (El Nido Ranch Road to the Lafayette Reservoir Access Road) Modified Road Diet Concept (Lafayette Reservoir Access Road to Risa Road) Figure 7: Modified Mount Diablo Boulevard Road Diet Concept There is sufficient right-of-way to accommodate this design by incorporating the existing sidewalk on the south side of Mount Diablo Boulevard. Page 7 of 9

8 3 Alternative School Stagger Time Scenario Currently, the two schools in Downtown are in session for the following times: Stanley Middle School: 8:15 AM 2:53 PM (except Wednesday, 9:24 AM 2:53 PM) Lafayette Elementary: 8:30 AM 2:42 PM (except Wednesday, 8:30 AM 1:42 PM) We evaluated scenarios that shifted either Stanley or Lafayette Elementary one hour earlier to stagger the start times to try and relieve traffic congestion along Moraga Road. Currently, the peak hour of volume and congestion is between 8 9 AM. Shifting Stanley s start time one hour earlier would shift a portion of the congestion to the earlier period. This could make conditions worse for the overall morning commute by causing worse congestion earlier, which could spill over into later time periods. Based on feedback from the Steering Committee, we evaluated shifting the Stanley start time to 9:30 AM, as it currently starts on Wednesdays. Table 2 presents the existing traffic volumes on Moraga Road between 7 and 10 AM and the resulting volumes with the staggering of start times. The school trips are based on the estimates provided in the previous November 10th traffic memo. Table 2: School Staggered Start Times Volumes Scenario Total School- Related Vehicle Trips Moraga Road Volumes (two-way, peak hour) 7-8 AM 8-9 AM 9-10 AM Existing Volumes, Existing Start Times Shift the Elementary School to 7:30 AM Shift the Middle School to 7:30 AM Shift the Middle School to 9:30 AM - 1,500 2,100 1, ,820 1,780 1, ,080 1,520 1, ,500 1,520 1,780 This table shows how shifting the Middle School start time to 9:30 AM, or shifting the Elementary start time to 7:30 AM, would help de-peak the congested 8 9 AM peak hour. The Middle School start time could be shifted to a time between 9:00 to 9:30 AM to achieve these benefits. Page 8 of 9

9 4 Recommendations The key recommendations from this analysis are: The School Street One-Way Westbound concept should be added to the Short List for consideration by the Steering Committee. The concept provides a modest improvement on congestion with limited trade-offs. The alternative Mount Diablo Road Diet conceptual design with two westbound travel lanes and one eastbound travel lane should replace the previous concept with one travel lane in each direction. The alternative concept satisfies the original goals of the concept and can still be accommodated within the right-of-way. A staggered start time concept that shifts the Middle School start time to between 9:15 or 9:30 AM should be included in the Short List strategy definition as the analysis indicates there congestion reduction would result. Page 9 of 9