Glossary of Terms

% of Units Below Market Rate (BMR): We currently have more dedicated affordable housing developments than market rate developments, where rents are subsidized below market rate. Many developments were 100% affordable, meaning that all of the units were subsidized; other developments had inclusionary units, where some units were set aside for low-income households, but the rest of the units were market rate. Some developments were 100% market rate with no affordable units designated.

Assigned parking: Parking is “assigned” if households have a designated space that is reserved for their exclusive use. The database shows the % of assigned spaces out of the total parking spaces provided.

Average Monthly Rent: The average monthly rent was provided by the property managers. For sites with inclusionary affordable units, we used a weighted average of the market rate rent with the affordable units’ rent.

Below Market Rate (BMR) units: Affordable housing is subsidized to allow reduced rents for low-income households. The income level of the household is restricted as a proportion of Area Median Income (AMI), which is determined annually at the county level. We put BMR units into categories of Extremely Low Income (below 30% AMI), Very Low Income (between 31-50% AMI), Low Income (51-80%, but divided into two categories as some developments have a further threshold of 60% AMI), and Moderate Income (81-120% AMI) to match the income categories used by affordable housing developers. 

Car sharing: Some developments have car sharing on site, others offer discounted memberships, and some have car sharing nearby, but with no direct affiliation. We used GIS (geographic information systems) layers to indicate how far away the nearest car share car is located from the site. The name of the car share service is given as well. The map shows icons for car share locations and for transit boarding opportunities.

Cost of parking: We counted parking spaces at each site and categorized spaces by category: surface, garage, and underground. The Cost of Parking on the building report reflects the number of spaces of each type and the corresponding cost of construction. The costs of empty parking spaces were calculated according to the mix of parking at each site. The table below shows the values we used to calculate the cost of empty spaces.

Source: Our costs do not explicitly include the cost of land but do reflect a relatively higher cost compared to the baseline costs cited in the national VTPI report. We have verified with developers participating in this study that these costs are in the ballpark of what today’s Bay Area developers are paying in 2014. Todd Litman, VTPI (and GreenTRIP Advisory Committee member) puts surface parking at $10,000/space, garage at $20-40,000/space (p. 5.4-17.) We don’t currently have a cost for bike parking. Litman estimates it at 5% of a car parking space (p. 5.4-22).

Type of Parking Spaces Cost
Surface Spaces (outside uncovered, or with canopy, but not enclosed, on-site and off-street) $20,000
Garage Structured Spaces (enclosed within a common garage at street level or above) $50,000
Underground Spaces (below street level, including partially underground) $80,000

Development Type: Our data collection included multi-family residential only and mixed-use sites, where some commercial or office uses were combined with residential. Mixed-use sites provide opportunities for shared parking between compatible uses where the peak parking times are different. 

Map on building report: The map shows the location of the building and the surrounding area, with a ¼ mile radius circle and a ½ mile radius circle. Transit stops and car share locations are on the map, and the user can zoom in and out and use street view to see the site. Satellite map layer can be turned on and off.

Number of total parking spaces: This was calculated for each site by adding the number of spaces for exclusive use for residential parking with the number of spaces shared by non-residential and with on-site residential uses. Some mixed-use sites have lower occupancy of parking in the middle of the night due to daytime (commercial or office) uses being closed, and we wanted to recognize sites that were sharing commercial spaces with residential uses where that was happening.

Parking Type: see Cost of Parking.

Place Type: MTC’s place types were used to group areas with similar land use patterns. Visit MTC's website for a more detailed definition of the 7 regions. They include: Regional Center, City Center, Suburban Center, Transit Town Center, Urban Neighborhood, Transit Neighborhood, and Mixed-Use Corridor. If a project fell within or near a PDA with an assigned place type we applied that place type to the project. The purpose is to make it easy for users to find similar projects by place type even if their particular city of interest doesn’t have a project in the database that represents that city. Conversely, larger cities have multiple place types so searching by all projects within a city is increasingly less relevant as cities move toward more context specific parking requirements.

Priority Development Areas: The PDAs are designated in Plan Bay Area in the GIS Data Catalog, and each jurisdiction was able to determine where PDAs were placed. PDAs are designed to handle the majority of future development during the life of Plan Bay Area. This list is from MTC and ABAG.

Resident Type: For affordable housing developments, there is sometimes a designation of the population that is targeted based on the type of funding that contributed to building the project and as a result units are restricted to designated resident types, including requiring a minimum number of people for larger units, and providing services specific to that segment of the population (such as senior health services for senior developments or child play areas for family developments). For market rate, there is typically no designation; an exception is senior facilities.

Size of parking space: We used the industry standard of 300 square feet per parking space. This includes drive aisles and space for maneuvering. Standard parking space dimensions are 9 feet by 19 feet. This can be more or less depending on the city or type of space (such as compact, oversized, disabled). Source:, Victoria Transport Policy Institute, 2013.

Spaces available per unit: This is the supply of residential parking provided/built as a ratio. This is a common measure of parking required in an area or city.

Spaces used per Bedroom: This is the observed use demand of residential parking, taking into account the size of the unit and number of bedrooms. We recognize that larger units housing more people may use a greater number of parking spaces. By calculating the number of bedrooms, we hoped to create a measure that would better reflect the parking demand use of larger households.

Spaces used per Unit: This is the demand observed use of residential parking at this site as a ratio. 

Subregion: This GIS layer was created by TransForm to differentiate the variation of development to make it easy to find projects by sub divisions within the East Bay real estate market in particular. We divided Contra Costa and Alameda Counties along the geographic division of the hills and grouped the areas in the south, west and east together, as the similarities defy county lines into “Inner East Bay”, “Central/East Contra Costa County and Tri Valley” and “Southern Alameda County”. All the North Bay Counties are grouped together for now and we will reconsider subregional boundaries after learning user preferences and needs.

Surrounding Street Parking: Property managers and data collectors determined reported on whether the streets surrounding each site are time restricted, metered or residential parking permitted parking areas. New data is availble from MTC in the Regional Parking Database for some locations.

Traffic Reduction Strategies: The GreenTRIP Certification program encourages three main traffic reduction strategies proven to result in the greatest reduction in traffic: free or discounted transit passes, car share with free or discounted membership, and unbundled parking (see definition below). We collected data from projects actively implementing on these three strategies as well as on available number of bike parking spaces, shuttles, transit screen information provided, ad proximity to existing Bay Area Bike Share pods. We distinguish between availability of strategies by location and active provision of subsidies to reduce the cost of passes or carsharing memberships.

Transit Access Score: The Transit Access Score is an overall transit index that looks at connectivity, access to land area and jobs, and frequency of service.  It is an index ranging from 0 to 10 (10 is best). This score relies on the combination of several measures to consider the share of transit commuters, household type and other locational variables such as household density and walkability. More information on CNT's Transit Score is here starting on p. 29.

Transit Passes: Some developments have discounted or free transit passes available for residents. If so, it is indicated in the Comparison Report and on the building report. We have also indicated the type of transit that is available and the distance to board that transit.

Transit Screen: A real time display on a computer screen of transit availability in the area near the development.

Unbundled Parking: Charging for parking separate from rent is “unbundling.” We indicate what percentage of available spaces on site are “unbundled” and what that charge is (monthly or annually).

Unit Size: Any units with more than three bedrooms were included in three + bedroom unit totals.