Traffic on the roads results from individuals deciding where, when, and how to travel. Decisions such as where to live, work, and shop also impact travel behavior. A travel demand model is a set of mathematical procedures and equations that represent the variety of transportation choices people make, and how those choices result in trips on the transportation network.
TRPC maintains two types of travel demand models for Thurston County. The models have a base year of 2018, and a future year of 2045.
The regional model is a traditional 4-step model developed in the EMME platform. The four steps are:
How many trips and for what purpose do each household produce?
What are their destination choices?
What mode of travel do they use for each trip?
What is the route they take for each trip?
The regional model includes all of Thurston, Grays Harbor, and Lewis counties, and parts of Pierce and Mason Counties. TRPC and its partners use the regional model to identify and implement a coordinated transportation vision across jurisdiction boundaries. The model is ideal for studying:
Major transportation investment studies
Regional land use and transportation policies
Traffic impact studies
Travel demand management and commute trip reduction strategies
TRPC's dynamic traffic assignment (DTA) model is developed in the Dynameq platform. This model covers Thurston County and parts of Pierce and Lewis counties. The DTA model is integrated with the regional model, sharing a common zone structure, network, and travel demand.
The DTA model simulates the movement of individual vehicles on lanes with car-following models, gap-acceptance models, and explicit signal timings. The models focus on route choice by simulating individual driver response to other drivers and roadway/intersection design and provide more realistic estimations of congestion and delay. This finer scaled makes it ideal for evaluating: