SAN FRANCISCO COUNTY TRANSPORTATION AUTHORITY
San Francisco is a major hub for jobs in the Bay Area and one of the densest cities in the United States. Many residents, workers, and visitors rely on the City's streets to get them where they need to go - whether that is in a car, in a bus, or on a bike. Traffic congestion slows down these trips, which can mean more people spending more time in transit, more vehicle pollution, and more greenhouse gases emitted for each trip.
Vehicle miles traveled represents the total amount of driving in an area. The vehicle miles traveled in San Francisco increased following the 2008-2009 recession. San Francisco has a strong backbone of regional transit, but the economic upturn has resulted in increases in vehicle miles traveled since 2011, resulting in increased congestion and decreased vehicle speeds during peak periods over that timeframe.
Vehicle speed is one way to measure traffic congestion. The City monitors vehicles speeds along the Congestion Management Network, which includes major driving routes in San Francisco. Average speed is measured separately for urban arterial streets and freeways. It is measured during the morning and evening “peak periods,” or rush hours.
AVERAGE SPEED DURING RUSH HOUR
The San Francisco County Transportation Authority (SFCTA) conducts the Congestion Management Program, which is a bi-annual program conducted in accordance with state law to monitor and mitigate traffic congestion. The Congestion Management Program monitors performance on a network of important driving routes in the city, and links transportation network performance to transportation decisions that are made to inform better land use and investment decisions.
Efforts across the City to improve performance of the road network include robust travel demand management (TDM) programs, land use and transportation planning projects to prioritize development and investments across the city and region, and funding and delivering transit and highway infrastructure projects to support near- and long-term transportation needs.
In addition to the average speeds of all vehicles on the road, data is available on the speed of transit vehicles, which is used to calculate a Transit-to-Auto Ratio. This ratio provides a direct comparison of auto and transit travel speeds. If the Transit-to-Auto Ratio is 2, then travel times on transit are twice as long as in a private vehicle for the same length trip (i.e., private vehicles are twice as fast).
TRANSIT-TO-AUTO TRAVEL TIME RATIO
How Performance is Measured
The AM peak period is defined as 7:00 a.m.-9:00 a.m., and PM peak as 4:30 p.m.-6:30 p.m. Congestion monitoring is conducted in the spring season, and is scheduled to take place at times that are representative of overall traffic conditions. Monitoring is scheduled to avoid holidays, during periods when school is out of session, or during major events.
Transit-to-Auto ratios are calculated on CMP segments where at least 50% of the segment is covered by a transit route. The overall ratio is calculated as the weighted average by length of segment for all segments.
The SFCTA uses INRIX data, a commercial dataset which combines several real-time GPS monitoring sources with data from highway performance monitoring systems, as the primary source for official speed and Level of Service (LOS) calculations. INRIX data is supplemented with floating car data where INRIX data is not available. This method was adopted in the 2013 CMP after initial conducted as part of the 2011 CMP found that results calculated from INRIX were appropriate for use in speed and LOS calculations. The 2011 analysis found that speeds from INRIX data were, on average, higher than speeds from floating car runs, but fell within the range of variability of floating car results for a given segment and time period. Prior to 2013, the SFCTA used the floating car method to collect travel time data on the CMP network.
The number displayed on the scorecard page represents the most recent data from the average speeds chart above.
- Read about the Congestion Management Program on SFCTA’s website.
- Learn more about congestion throughout the region on the Metropolitan Transit Commission’s Vital Signs website.
Please click first on the chart above and then click the “Download” button in the bottom right corner of the visualization to view and download the data displayed in the chart.