Southern California Association of Governments (SCAG) developed
the Heavy Duty Truck (HDT) Model to evaluate important policy
choices and investment decisions. The HDT model is a primary
analysis tool to support the goods movement policy decisions made
by SCAG and regional stakeholders.
About SCAG’s HDT
As part of 2012-2035 Regional Transportation Plan/Sustainable
Communities Strategy (RTP/SCS), the HDT model focused on
analytical needs to support project and policy planning in the
following key areas:
Port Access Improvements
Clean Technology Truck Lanes
Freight Facility Developments and Land Use Strategies for
Goods Movement-Oriented Activity Centers (Inland Ports,
Freight Villages, new inland warehouse, and distribution
Air Quality/Conformity Analysis
Economic Impact Analysis
Operational Strategies (port and highway)
The model development process included a thorough review of the
HDT model by an expert panel that ranged from academics to
Consultants. The HDT model was validated by comparing the overall
vehicle miles traveled (VMT) for individual counties and air
basins against the data obtained from the Highway Performance
Monitoring System (HPMS).
Click on the Features and Framework of SCAG’s HDT Flow
Chart for additional information.
The model documentation includes further information on the
HDT Model Structure: The model forecasts trips for three HDT
weight classes: light-heavy (8,500 to 14,000 lbs. gross
vehicle weight (GVW); medium-heavy (14,001 to 33,000 lbs.
GVW); and heavy-heavy (>33,000 lbs. GVW
Internal HDT Model Development: This includes the development
of all HDT trips that have both origins and destinations
within the six-county modeling area.
Port Model Development: This includes the port model
development that predicts the HDT trips coming out of and
going into the San Pedro ports, which includes the Port of
Long Beach (POLB) and Port of Los Angeles (POLA).
External HDT Model Development: This includes how the
external HDT trips are captured in the HDT model that come
into, go out of, and pass through the region.
Intermodal Trip Tables: This includes how the intermodal trip
tables were derived and integrated with the HDT model.
Time-of-day Choice: This includes the derivation of time of
day factors from various sources.
HDT Model Calibration and Validation: This includes
validation data, procedures and results from various
SCAG’s Goods Movement Program seeks
to optimize the region’s transportation system through increases
in economic efficiency, congestion mitigation, safety and air
quality improvements, and enhancements to system security. In
doing so, all modes of freight are being evaluated, ultimately
resulting in a series of new recommendations and policies
regarding infrastructure improvements.