Transportation

Transit ridership refers to the number of passenger boardings on public transportation, which includes buses, trains and ferries. Transit ridership can be measured in a variety of ways, including in terms of weekday boardings or in terms of annual boardings for a typical resident (per capita).

Commute patterns, also known as county-to-county commute flows, refer to the number of individuals traveling within, between and outside of the nine counties of the San Francisco Bay Area for work.

Commute mode choice, also known as commute mode share, refers to the mode of transportation that a commuter uses to travel to work on a typical workday, such as driving alone, biking, carpooling or taking transit.

Transit cost-effectiveness refers to both the total and net costs per transit boarding, both of which are adjusted to reflect inflation over time. Net costs reflect total operating costs minus farebox revenue (i.e. operating costs that are not directly funded by system users).

Daily miles traveled, commonly referred to as vehicle miles traveled (VMT), reflect the total and per-person number of miles traveled in personal vehicles on a typical weekday.

Commute time refers to the average number of minutes a commuter spends traveling to work on a typical day.

Traffic volumes at regional gateways refers to the number of vehicles crossing county boundaries on a typical day to enter or exit the nine-county San Francisco Bay Area.

Transportation planners use what's known as a buffer time index, or BTI, to gauge the reliability of travel times along a given route. BTI is a measure of how much time (over and above the average travel time) a driver would have to budget to be 95 percent sure of arriving on time at his or her destination. BTI is expressed as a fraction of the average travel time: the lower the BTI, the more reliable the trip. This measure covers freeways only, as no comparable data are available for local streets or the transit network.

Miles traveled in congestion reflects the share of miles traveled on regional freeways in congestion for a typical weekday; it is often referred to as the congested share of freeway miles driven (also referred to as vehicle miles traveled, or VMT). Congestion is defined as speeds less than 35 mph, the level at which freeway throughput is maximized.

Time spent in traffic congestion - also known as congested delay - refers to the number of minutes weekday travelers spend in congested conditions in which freeway speeds drop below 35 mph. Total delay, a companion measure, includes both congested delay and all other delay in which speeds are below the posted speed limit.

Transit asset condition reflects the relative age of the region's transit infrastructure. Vehicle condition is measured by the vehicle's age relative to its specified useful life. Condition of guideway is measured by the share of miles that have speed restrictions due to aging infrastructure. Condition of facilities is measured by the share of facilities with a condition rating below fair, weighted by the monetary value of the facility.

Highway pavement condition, measured by the share of highway lane-miles flagged as distressed by Caltrans, reflects the regional pavement quality on the highway system.

Street pavement condition, more commonly referred to as the pavement condition index (PCI), reflects the quality of pavement on local streets and roads in the region. Calculated using a three-year moving average, PCI ranges from zero (failed) to 100 (brand-new), and has been used as a regional measure of pavement quality for a decade and a half.

Bridge condition here is measured by the share of bridge and overpass deck area rated as “Poor” according to the FHWA’s National Bridge Inventory (NBI) condition ratings, which account for ratings of the bridge’s deck, superstructure, substructure or culvert.