From Metro's press release:
"Research shows that a few key measures can strongly predict the readiness of an area to support walkable, mixed-use development and help residents live a lifestyle with less reliance on a personal automobile. Metro's Transit-Oriented Development Program's new transit orientation measure is a composite of these important elements.
The five P's of transit-oriented development
Traditionally, true transit-oriented development has been said to possess three D's – density (residential and/or employment), diversity (e.g. mix of uses, ages, income groups) and design (pedestrian scale and orientation). For the purpose of better capturing "urban character" in a composite measure, a more holistic view of the transit friendliness of station areas and corridors is proposed."
Thanks to Christopher Yake