Item No. 1
Town of Atherton
CITY COUNCIL STAFF REPORT – STUDY SESSION
TO: HONORABLE MAYOR AND CITY COUNCIL
GEORGE RODERICKS, CITY MANAGER
FROM: ROBERT OVADIA, PUBLIC WORKS DIRECTOR
DATE: SEPTEMBER 4, 2024
SUBJECT: RECEIVE AN UPDATE AND PROVIDE FEEDBACK ON THE
ALAMEDA DE LAS PULGAS / ATHERTON AVENUE
ROUNDABOUT ANALYSIS
RECOMMENDATION
It is recommended that the Council provide feedback and direction regarding the feasibility analysis of a roundabout on Alameda de las Pulgas at Atherton Avenue.
BACKGROUND
The Alameda de las Pulgas corridor which connects Redwood City to Menlo Park and Palo Alto, through the Town of Atherton, and unincorporated San Mateo County is a high traffic corridor that serves as a north-south alternate to El Camino Real. Pass-through traffic has been measured to be between 60% to 89% of the overall traffic volume. Residential streets are impacted as commuters attempt to find alternative routes around congested roadways during peak hours, particularly around the Atherton Avenue intersection which is four-way stop controlled.
The Alameda de las Pulgas corridor was evaluated in two separate studies in 2019. The Alameda de las Pulgas Corridor Traffic Study reviewed existing conditions along Alameda de las Pulgas and recommended several improvements, both within and outside of Town limits. The Local Traffic Flow/Long Range Planning Solutions Study evaluated existing traffic operations and origin-designation patterns and recommended short- and long-term measures for efficient circulation. Additionally, it has been determined through these studies that the all-way stop intersection of Atherton Ave and ADLP currently operates at a level of service (LOS) F with delays up to 92 seconds during the peak hours and that signalizing this intersection will improve operations to LOS B with projected delays less than 18 seconds.
The corridor study also advised that a roundabout at the Atherton Avenue intersection would also significantly reduce vehicle delays. Though a full analysis was not completed at the time, in consideration of the limited right-of-way at the intersection, the study recommended the ADLP/Atherton Avenue Roundabout Analysis
SEPTEMBER 4, 2024
installation of a traffic signal rather than a roundabout at the intersection.
Following City Council discussion at its March 6, 2024, meeting, staff issued a task order to Interwest Consulting Group (Interwest) to evaluate the feasibility of a traffic circle, roundabout or mini-roundabout at the Alameda de las Pulgas / Atherton Avenue intersection.
ANALYSIS
In evaluating the feasibility of a potential roundabout, Interwest reviewed existing conditions, accident history, level of service and various design considerations.
Existing conditions:
• Alameda de las Pulgas is a minor arterial with a speed limit of 30 miles per hour, features a Class II bikeway (dedicated bike lanes), is served by two bus stops on the north leg of the intersection, and has various utilities located in and around the intersection. o It is noted that the Alameda Traffic and Safety Improvements Project will adjust lane widths and bicycle lane configuration along the Alameda de las Pulgas corridor.
• Atherton Avenue is a local collector street, with a speed limit of 30 miles per hour east of the Alameda de las Pulgas intersection and 25 miles per hour to the west of the intersection.
The roadway is currently marked as a Class III (shared use) bikeway east of the intersection, with a designation as a future Class II facility (dedicated bike lanes) in the bicycle and pedestrian master plan.
Collision History:
• Two collisions were noted at the intersection between January 1, 2019, and December 31, 2023. One, in May 2022, located approximately 60 feet south of the intersection, involved a bicycle and a vehicle and resulted in suspected minor/visible injury. The other collision involved a vehicle with object. Both collisions were determined to be related to speeding.
Traffic Analysis:
• The intersection is currently stop controlled.
• Per the Alameda de las Pulgas Corridor Study, prepared by AMG, the current Level of Service (LOS) is at F, with delays of approximately 1.5 minutes southbound in the morning peak and northbound in the afternoon peak. The study concludes that the implementation of a roundabout, or traffic signal would significantly reduce vehicle delays and improve the Level of Service at the intersection.
Findings:
Interwest reviewed various alternatives for the roundabout and concluded that, if a roundabout is to be implemented, a single-lane roundabout with a non-traversable central island (with truck apron), raised splitter islands, mixed use pathways and separated pedestrian crossings would be most appropriate. Raised truck aprons are proposed to be provided to accommodate turning movements of larger trucks and emergency vehicles. An illustration of a standard configuration is shown in Attachment 1.
ADLP/Atherton Avenue Roundabout Analysis
SEPTEMBER 4, 2024
Interwest recommends the following for the layout of the roundabout:
• Inscribed diameter of traffic lane (outside edge to outside edge) = 90 feet • Travel lane width (within the roundabout) = 12 feet
• Truck apron width (to accommodate truck and emergency vehicle turn movements) = 15 feet
• Truck apron height = 3-inches, with rolled curb
• Raised splitter islands to separate traffic and provide pedestrian refuges for street crossings • Mixed uses pathway (10 feet wide minimum), with ramps to and from bike lanes, around each corner
The analysis also identifies several constraints as follows:
• Right-of-way/property acquisition – the conceptual design shows that a roundabout can be accommodated at the intersection with nominal acquisition, predominantly at the northwest and southeast corners. Interwest believes that the need for right-of-way can be reduced or eliminated with minor adjustments in the layout during the design process by slightly changing the shape of the roundabout, making it a little more oval in shape. • Major utility conflicts – in addition to some minor utility adjustments, there a couple of significant utility conflicts that will require significant coordination and resources to accomplish. These include:
o Electrical transmission pole relocation (northwest corner) o Communications infrastructure relocation (southeast corner) • Bus stops – there are two bus stops located north of the intersection that will need to be considered in the final design
• Drainage system – drainage system modifications in the intersection will be needed to align with the reconfiguration of the intersection and to coordinate with green infrastructure improvements
• Environmental impacts and considerations – The Town is currently working with Caltrans regarding potential impacts of the Alameda de las Pulgas Corridor Traffic and Safety Improvements Project. Concerns have been raised regarding potential impacts to cultural resources associated with the proposed traffic signal and intersection reconfiguration. The environmental review is still pending. The potential impacts associated with the increased footprint of the roundabout would need to be analyzed.
• Costs – the preliminary cost estimate for the roundabout is quite a bit higher than the estimated cost of the traffic signal installation, approximately $500,000, not including design costs.
The implementation of a roundabout would have several additional impacts that were not included in the analysis. These include, but are not limited to:
• Additional stormwater treatment/green infrastructure areas required along Alameda de las Pulgas and in the area of the intersection to accommodate regulatory requirements associated with the creation and replacement of impervious areas. • Though property acquisition may be reduced/eliminated through final design, there will be impacts to property frontages and frontage improvements associated with the roadway realignment and widening required to implement the roundabout.
ADLP/Atherton Avenue Roundabout Analysis
SEPTEMBER 4, 2024
• Access impacts – the implementation of the roundabout would also impact driveway access. The splitter islands (raised and marked) would restrict left turns in and out of driveways along both Atherton Avenue and Alameda de las Pulgas. • Noise impacts – noise impacts are anticipated at the intersection related to truck movements as they traverse the roundabout and truck apron.
• Lighting impacts – It is recommended that the Town consider the installation of streetlights to improve visibility of pedestrians crossing the street. Installation of Rectangular Rapid Flashing Beacons (RRFB’s) may also be considered to further advise traffic of pedestrians crossing the street.
• Grant Impacts – The grant received for the Alameda de las Pulgas Traffic and Safety Improvement project requires obligation of federal funds for construction by Fall 2025.
The current project schedule forecasts construction beginning in summer 2025, in advance of the obligation deadline. It is unclear if the grant would cover the roundabout as the initial project description included a traffic signal at the intersection. Further, the implementation of the roundabout will require environmental, right-of-way and utility clearance and certification by Caltrans in advance of requesting obligation of construction funding. This will further extend the timeline of the project. Coordination is required with both AT &T and PG&E to facilitate relocation of utility infrastructure. The process and timelines associated with utility relocations, particularly with PG&E is not timely. It is noted that a power connection would be required from PG&E for the traffic signal alternative.
Public engagement:
• Outreach letters – Prior to initiating the evaluation of the roundabout, the Town sent letters to the properties directly adjacent to the intersection to gauge interest and concerns regarding the potential roundabout. Two property owners reached out via phone after receiving the letter. One resident, though supportive of roundabouts in general, was opposed to a roundabout in this location. The other resident did not respond after several attempts at contacting.
• Public outreach meeting – a public outreach meeting associated with the Alameda de las Pulgas Traffic and Safety improvements project was held on June 20, 2024, to review the conceptual design of the project. Approximately 12 members of the public attended the meeting. The conceptual design outlined proposed improvements along the corridor including lane width reductions and modifications to allow for buffered bike lanes, as well as traffic signals at the Camino al Lago and Atherton Avenue intersections. Additionally, attendees were advised that we were also evaluating the possibility of a roundabout at the Atherton Avenue intersection. Two residents expressed opposition to a traffic signal at the Atherton Avenue intersection and asked what problem we were solving as they did not see a significant issue at the intersection. They were more supportive of the idea of a roundabout than a signal at the location.
• The conceptual design for the Alameda de las Pulgas Traffic and Safety Improvements, along with the conceptual roundabout layout, were also presented to the Transportation, Bicycle and Pedestrian Safety Committee. The Committee was supportive of the roundabout concept.
• Public education may be needed regarding roundabouts and how to navigate.
ADLP/Atherton Avenue Roundabout Analysis
SEPTEMBER 4, 2024
FISCAL IMPACT
None at this time. Additional costs will be incurred for the design and construction of the roundabout. Should the Council desire to pursue the design of the roundabout, staff will seek guidance from Caltrans regarding the potential and process for revising the scope of the grant to allow for a roundabout at the intersection.
GOAL ALIGNMENT
This Report and its contents are in alignment with the following Council Policy Goals:
• Goal Area A – Maintain Fiscal Responsibility
• Goal Area B – Preserve Small Town Character and Quality of Life • Goal Area D – Manage Circulation and Improve Safety
• Goal Area F – Be Forward-Thinking, Well-Managed, and Well-Planned
POLICY FOCUS
The Council policy focus should be on the desire to improve public, pedestrian, and bicycle safety, and traffic flow along the Alameda de las Pulgas corridor. In addition, the Council will need to consider impacts on grant funding, locally required funding, and project timing.
PUBLIC NOTICE
Public notification was achieved by posting the agenda, with this agenda item being listed, at least 72 hours prior to the meeting in print and electronically. Information about the project is also disseminated via the Town’s electronic News Flash and Atherton Online. There are approximately 1,200 subscribers to the Town’s electronic News Flash publications. Subscribers include residents as well as stakeholders –to include, but be not limited to, media outlets, school districts, Menlo Park Fire Protection District, service provides (water, power, and sewer), and regional elected officials.
COMMISSION/COMMITTEE FEEDBACK/REFERRAL
This item has not been before a Town Committee or Commission
ATTACHMENTS
1. Roundabout Feasibility Report
2. Utility and right-of-way photos
3. Conceptual layout of the traffic signal option