Cars headed toward San Francisco on the freeway

Northbound I-280 Transit and Carpool Lane Study


The project goals for the Northbound I-280 Transit and Carpool Lane Study are to promote carpooling and transit use, enhancing reliability and efficiency for local and regional travelers and public transit riders, while incentivizing these sustainable modes. Creation of a transit/carpool facility on I-280N would help advance regional transportation goals and San Francisco’s freeway management strategies, while maintaining safety and access for all travelers.  It would also better integrate San Francisco County into the peninsula US101/I-280 and Broader Bay Area carpool/Express Lane network.

Project Objectives 

  • Increase person throughput (number of people traveling)
  • Promote equitable carpooling and transit use
  • Enhance carpool and transit travel time and reliability
  • Limit impact on General Purpose lanes and traffic diversions to local streets
  • Extend regional transit and High-Occupancy Vehicle (HOV) benefits into San Francisco

Design Options

The project includes two main transit/carpool lane design options under consideration for the relatively short segment (<1 mile) at the northern terminus of I-280N from the 18th Street overcrossing to King/5th Streets:

  • Option 1: I-280N Left-side Traffic Lane Conversion – Changing the existing (left side) #1 general purpose lane to transit/carpool use only, with #2 (right side) lane remaining a general purpose lane
  • Option 2: I-280N Shoulder Conversion – Changing the existing left side freeway shoulder to transit/carpool lane use via striping (not physical widening of the roadway), leaving the #1 and #2 freeway traffic lanes for general purpose traffic use.  

Given the short length of these segments, the project can be considered “operational” in nature to give buses and carpools access to signalized intersections “at the front of the line” as is provided for bicycles or other road users on some surface streets and arterial state routes. (See corresponding image below)

Two sets of lane diagrams, with lines indicating on a map which parts of I-280 they correspond to. The first set of lane diagrams represent options for northbound I-280 before the 6th Street off-ramp, and show the existing setup (from left to right: a wide shoulder, 4 general-purpose lanes, and a narrow shoulder), Option 1 — Lane Conversion (from left to right: a wide shoulder, a new HOV lane, 3 general-purpose lanes, and a narrow shoulder), and Option 2 — Lane Addition (from left to right: a narrow should
SH = Shoulder, GP = General Purpose, HOV = High Occupancy Vehicle

The project also considers the possibility of extending either of the above configurations onto King Street to further prioritize public transit and carpools as they continue on local streets. This could be done by converting the #1 general purpose lane on northbound King Street from 5th Street to 3rd Street. One key aim is to enable Muni and SamTrans buses and eligible shuttles to access the existing red transit lanes on 3rd Street and on Mission Street as buses head to connecting services at the Salesforce Transit Center.

A set of lane diagrams, with a line indicating on a map which parts of King Street they correspond to. The diagrams represent options for King Street between 3rd Street and 5th Street, and show the existing setup (from left to right: 3 general-purpose lanes), Lane Conversion (from left to right: a new HOV lane, an 2 general-purpose lanes)
SH = Shoulder, GP = General Purpose, HOV = High Occupancy Vehicle

Timeline and Status

  • May 2022

    Project Initiation 

  • November 2023 – January 2024

    Public Outreach 

  • Summer 2024

    Public Outreach — present evaluation results

  • 2025


  • 2026


2022 – 2024: Project Analysis, Environmental Document, and Approval

  • Concept refinement and alternatives analysis: Two main transit and carpool lane design options are under consideration in the northbound direction
  • Public and stakeholder engagement: We held Round 1 outreach to introduce the study project options from November 2023 to January 2024, and once further analysis is complete, will conduct Round 2 to present evaluation results by summer 2024

2025-2026:  Design and Implementation

  • Implementation Plan: We hope to begin design in 2025 and construction in 2026, pending project approval and funding availability

Southbound 101/280 Transit and Carpool Lane

The Southbound direction of travel will be studied with a dedicated scope and conceptual design options. We anticipate bringing a request for funding to the SFCTA Board in Spring 2024.

Future Steps

Final design; procurement and construction. The project timeline is subject to approval and funding availability.

Please see the Reports and Documents tab for resources including project study reports. 

Key features

A managed lane is a type of freeway lane where access is restricted by occupancy, tolling or direction, such as a bus/HOV lane, high-occupancy toll lane/Express lane, or reversible lane to improve traffic flow and overall efficiency of the facility.

101/280 Potential Managed Lanes Location

Given the existing configuration of our freeways, the 2108 Freeway Corridor Management Study found that carpool or express lanes could be implemented in the below segments:

A map of the project boundaries
Southbound lanes

The existing configuration of the I-280 and US 101 freeways allows for the creation of a continuous lane by converting the left-most existing general purpose lane into a managed lane. A carpool or Express Lane could operate along I-280 between the intersection of 5th and King Streets and US 101, continuing through the interchange to US 101 into San Mateo County, covering a distance of about five miles in San Francisco proper. This extension would be the northern end of a 65-mile managed lane from San Francisco to Morgan Hill.

Northbound lanes

Because I-280 exits from the right side of northbound US 101, any carpool or Express lanes entering San Francisco from San Mateo county will likely end at or near the county line. However, the study identified an opportunity to provide priority for northbound carpools and buses for approximately one mile along I-280N headed into South of Market, from about 18th Street to 5th Street.

Regional map of the managed lanes

2018 Freeway Corridor Management Study Report Findings

Without any changes to the current operation of the freeways in San Francisco, buses and carpools will continue to be stuck in the same traffic as all other vehicles, providing travelers with no incentive to ride transit or carpool. Carpool or Express lanes could give transit and carpools a faster ride, incentivizing more efficient trips. Bay Area Express Lanes give drivers a choice to save time by paying a toll and reward carpoolers with the same time savings at a lower cost. 

Given the existing configuration of our freeways, the study found that carpool, transit, and express lanes could be implemented in a few segments. Further analysis helped us identify Northbound Alternatives for a transit and carpool lane.

This project would help keep us aligned with regional goals and the Transportation Authority’s freeway management strategies, while maintaining safety and access for all travelers.  

The next phase includes transportation analysis and signal and roadway design tasks to evaluate and optimize project concepts.

Project Initiation

In October 2019, Caltrans approved the Project Initiation Document for the implementation of managed lanes along US 101 and I-280 in both San Francisco and San Mateo counties which identified the project scope of work and recommended design alternatives, based on a preliminary evaluation of traffic data, existing geometric constraints, cost, schedule, risk, environmental considerations, and benefits.

The 2018 study evaluated four managed lane options:

  1. No Build: The configuration of freeways remains as it is today.
    The study found that under this scenario, congestion continues to get worse, with some bottlenecks resulting in an additional 2 to 5 minutes of travel time over existing conditions. Despite this, there remains no incentive to use transit or carpool in the corridor, as both buses and carpools remain subject to these increasing delays.
  2. HOV2+: High Occupancy Vehicle (carpool) with a two-person minimum requirement.
    The study found that this option is not expected to provide travel time savings to transit riders and carpools and should not advance to further study.
  3. HOV3+: High Occupancy Vehicle (carpool) with a three-person minimum requirement.
    The study found that this option creates substantial additional congestion in the corridor, reduces person throughput, and should not advance to further study. Subsequently, the Transportation Authorization Board requested the staff to further evaluate the HOV3+ option for the study corridor due to the traffic pattern change during COVID-19.
  4. HOT3+: Express Lane with a three-person minimum carpool requirement.
    In this scenario, transit and carpools of three or more can access the lane at no cost. A demand-based, variable toll will be available to others who may pay to access the lane. The study found that this option could advance the goals of this study and warrants more detailed evaluation in subsequent study phases. In addition, important public policy concerns related to the equity impacts of express lanes should be considered, studied further, and mitigated.

 Please see the Reports and Documents tab for resources including project study reports. 

Public engagement

2023 - 2024 Outreach Events

The Transportation Authority is working with Caltrans, residents in districts 6 and 10, community organizations and businesses. 

We are conducting Round 1 of public outreach until January 31, 2024 for our Northbound I-280 Transit and Carpool Lane, which seeks to provide priority for public transit and carpools at the I-280 northern terminus at King Street, as traffic congestion on the busy corridor exceeds pre-pandemic levels.

The study team is available to meet with interested groups for community meetings through January 2024. 

Previous Events 

Virtual Town Hall Meeting

Date: Wednesday, November 15, 2023

Community members had the opportunity to learn more, ask questions, and tell us what improvements they wanted to see in near Northbound I-280 Transit and Carpool Lanes. 

Presentation (PDF)


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