Contact: Eric Young, San Francisco County Transportation Authority 
Office: 415-522-4816
Cell: 415-306-4509

Download this press release (PDF)

Job and population growth responsible for remainder of city’s worsening congestion

The San Francisco County Transportation Authority has released “TNCs & Congestion,” a report providing the first comprehensive analysis of how Transportation Network Companies Uber and Lyft collectively have affected roadway congestion in San Francisco.

The report found that Transportation Network Companies accounted for approximately 50 percent of the rise in congestion in San Francisco between 2010 and 2016, as indicated by three congestion measures: vehicle hours of delay, vehicle miles traveled, and average speeds. Employment and population growth were primarily responsible for the remainder of the worsening congestion. As a share of total congestion citywide, TNCs account for an estimated 25 percent.

(The TNCs and Congestion report follows the agency’s 2017 “TNCs Today” report that quantified the number and distribution of local TNC trips in San Francisco.) Major findings of the TNCs & Congestion report show that collectively the ride-hail services accounted for:

  • 51 percent of the increase in daily vehicle hours of delay between 2010 and 2016;
  • 47 percent of the increase in vehicle miles traveled during that same time period; and
  • 55 percent of the average speed decline on roadways during that same time period.
  • On an absolute basis, TNCs comprise an estimated 25 percent of total vehicle congestion (as measured by vehicle hours of delay) citywide and 36 percent of delay in the downtown core.

Notably, the report indicates that TNC activity affects congestion differently throughout the day and throughout the city. TNCs caused increased congestion across all times of day, including the morning peak, midday and evening peak, but the increase attributable to TNCs was most pronounced in the evening.

Consistent with prior findings from the Transportation Authority’s 2017 TNCs Today report, TNCs also caused the greatest increases in congestion in the densest parts of the city - up to 73 percent in the downtown financial district - and along many of the city’s busiest corridors. TNCs had little impact on congestion in the western and southern San Francisco neighborhoods.

The report also found that changes to street configuration (such as when a traffic lane is converted to a bus-only lane), contributed less than five percent to congestion.

“This report further quantifies the impact ride-hail services have on our streets,” said Aaron Peskin, Chair of the San Francisco County Transportation Authority and District 3 Supervisor. “It underscores the importance of our current collaboration with Transportation Network Companies to develop a per-trip tax to help mitigate the impacts of these trips, and informs our efforts to balance the availability of these new mobility options with our Transit First policies.”

Tilly Chang, Executive Director of the San Francisco County Transportation Authority, said: “Understanding the factors of congestion is key to our ability to address the problem effectively and maintain the accessibility of our downtown core. We are committed to data-driven analyses like this report to serve as the foundation for deeper understanding and informed action.”

How was report prepared?

The report utilizes INRIX data, a commercial dataset which combines several real-time GPS monitoring sources with data from highway performance monitoring systems and a unique TNC trip dataset provided to the Transportation Authority by researchers from Northeastern University.

These data are augmented with information on network changes, population changes, and employment changes provided by local and regional planning agencies, which are used as input to the Transportation Authority’s activity-based regional travel demand model SF-CHAMP. The work was performed by a team of researchers from the University of Kentucky and Transportation Authority staff.

How is congestion measured?

The TNCs and Congestion report uses the following common measures of roadway congestion:

Vehicle Hours of Delay: Measuring the overall amount of excess time spent in congestion, it is the difference between congested travel times and free flow travel times on a given roadway segment.

Vehicle Miles Traveled: A measure of the overall amount of travel, as measured in distance, that occurs on the streets.

Speed: The average speeds on streets.

Next steps

Agency staff will present the TNCs and Congestion report at the Transportation Authority Board meeting on October 16 at 10 a.m. in Room 250 of San Francisco City Hall.


Go to for:

  • Interactive map of data
  • Downloadable copy of “TNCs and Congestion”
  • Downloadable data file used to prepare “TNCs and Congestion”

Backgrounder on local and state agencies

Several government entities are involved in the planning, design, funding and regulation of San Francisco streets.

They include:

  • San Francisco County Transportation Authority: Funds a wide range of transportation improvements, monitors activity on city streets and adopts plans for mitigating traffic congestion in the city.
  • San Francisco Municipal Transportation Agency: Manages city streets, including parking and curb access; operates transit and regulates taxis.
  • California Public Utilities Commission: Regulates Transportation Network Companies statewide, including in San Francisco.
  • Caltrans: Owns some streets in San Francisco that are part of the statewide highway system, such as Van Ness Avenue and 19th Avenue/Park Presidio Boulevard.

About the San Francisco County Transportation Authority

The San Francisco County Transportation Authority’s mission is to make travel safer, healthier, and easier for all. We plan, fund, and deliver local and regional projects to improve travel choices for residents, commuters, and visitors throughout the city. The Transportation Authority Board consists of the 11 members of the San Francisco Board of Supervisors, who act as Transportation Authority Commissioners. Commissioner Aaron Peskin is Chair of the Board. Tilly Chang is the Transportation Authority’s Executive Director.