Wednesday, October 7, 2009

Traffic Report Part II: Higher Density = Less Traffic

The City’s Preliminary Traffic Impact Report presents the traffic impacts of three scenarios of development at Alameda Point: The General Plan, Alameda Point Revitalization Initiative Plan without traffic mitigations and the Initiative Plan with traffic mitigations.

(click on chart below for larger version)










The report uses 2,000 houses for the General Plan scenario and 4,599 for the SunCal scenario. Yet, in spite of the difference in the number of housing units, the AM Peak outbound traffic travel times with the Initiative with mitigations is, on average, anticipated to increase by only 21% (inbound is actually anticipated to decrease slightly).

How is this possible?

The answer lies in the type of residential units that would be built under the two scenarios. The General Plan scenario considers only single-family or duplex houses (the only type of units permitted under Measure A) while the SunCal plan includes a mix of housing types, including condos, townhomes, apartments, and live-work units. The inclusion of more compact housing types reduces automobile usage per unit. Take a look at some facts:

• Single-family detached houses generate an average of 10 car trips per day (a trip is defined as any time a car leaves or returns home) while condominium and townhouse residents average 5.6 trips per day. (Source: “Higher-Density Development, Myth and Fact. Urban Land Institute).

• Single-family homes average 2 cars per household compared with 1.3 cars per household for multi-unit households (Source: http://www.abag.ca.gov/services/finance/fan/housingmyths2.htm)

• People who live within ½ mile of transit are 10 times more likely to use it. (Source: Greenbelt Alliance)

• In the greater Bay Area, annual Vehicle Miles Traveled (VMT) by residents in Central Valley single-family homes is 32,000 compared to 15,000 for Bay Area Infill areas. (Source: Alameda Point Workshop III, August 7, 2008 presentation)

• The Rockridge area of Oakland, with a density of 14 households per acre, generates about half the VMT per household than does the Danville-San Ramon area, with a density of 3.8 households per acre (15,707 annual VMT vs. 31, 291 VMT). (Source: http://www.smartgrowth.org/library/cheers.html) .

• The SunCal plan includes a range of densities from 4.1 to 70 dwelling units (source: Specific Plan, table 311 and table 7-1) per acre and includes an array of housing types from large single-family homes to townhomes, live-work and multi-family.

Next: Take a Density Quiz