General Assumptions

Modeling Region

All of Ventura, Los Angeles and Orange Counties and portions of Riverside and San Bernardino Counties (containing over 90% of population of both counties). Imperial County is modeled via a separate demand model.

Zone System

Present day computers are not powerful enough to enable forecasts of individual persons or households. Instead persons are grouped by geography and income levels. The SCAG demand model aggregates population into 3191 zones largely defined by census tract boundaries. Within each traffic analysis zone (TAZ) population is divided into low, medium and high income segments.

Travel Modes

Automotive and local transit. Non-motorized trips are not modeled explicitly. See map.

Travel Purposes

Travel is divided into the following purposes:

• Home-based and non-home based, where a home-based trip is any trip starting or ending at a persons home.
• Home-based trips are subdivided as follows:
  • Home-based work (including trips by students to two or four year universities)
  • Home-based school (primary and secondary school trips)
  • Home-based other (all other home-based trips)
• Non-home based trips are classified as either work-based other (those trips not starting or ending at home), and other-based-other (all other trip types)