Primary Purpose
The Regional Travel Demand Model provides travel forecasting
capabilities for the analysis of SCAG’s plans and programs. The
current trip-based model was developed and adopted for the 2012
Regional Transportation Plan/Sustainable Communities Strategy
(RTP/SCS) analysis.
About the Trip Based Model
Network based transportation modeling is a mandated Federal
Conformity Rules requirement. The trip-based model was Peer
Reviewed in May 2011 and found consistent with the
state-of-the-practice. Currently, this model is the only approved
model for regional transportation plans and programs analysis
within the SCAG Region.
Features
SCAG’s trip-based model includes a very advanced mode choice
component capable of forecasting all travel modes within the
Region, including high-speed rail. Additional capabilities have
been added to capture pricing and the travel effects of smart
growth.
Framework
The model runs on the TransCad software platform and is based on
a four-step model structure, which includes trip generation, trip
distribution, mode choice, and trip assignment.
Inputs & Outputs
Inputs
- Transportation Analysis Zones (TAZs) (4,109 tier 1 zones,
11,267 tier 2 zones)
- Socioeconomic Data (population, employment, households,
workers, school enrollment)
- Highway network (70,000+ street segments, posted speed,
number of lanes, and functional classification)
- Transit network (2000+ routes/patterns, headway, service
hours, fares, stop locations)
- Seaports (heavy duty trucks)
- Airports (passenger and cargo trips)
- External (interaction with other regions and pass-through
trips)
Outputs
- Vehicle trips
- Traffic volumes
- VMT by link and geographic areas
- Trips origin/destination
- Trip length
- Mode shares
- Transit boarding
Documentation
SCAG Regional Travel Demand Model and 2012 Model Validation
