Subarea Models

Why We Develop Subarea Models

The major benefit of Dynamic Traffic Assignment (DTA) subarea models, compared to the traditional 4-step travel demand model, is the ability to simulate how drivers interact to congestion and how they respond.  The DTA model is capable of reading all file formats and data structures of the regional Emme macro model, and shares common zonal system, network, and travel demand.

The dynamic traffic assignment moves individual vehicles on lanes, with car-following models, gap-acceptance models, and explicit signal timings. In terms of scale, the Dynameq DTA model fits in between the regional macro model and micro simulation models, and is often referred to as a mesoscopic model. It enables modelling of:

  • Signal timing strategies,
  • Identification (place, and duration) and impacts of bottlenecks,
  • Intersection/roadway levels of service,
  • Intersection queuing of vehicles, and 
  • Vehicle propagation throughout the network

Interstate 5 – Yelm Traffic Simulation

In December, an Amtrak train derailed on Interstate 5 south of the Mounts Road interchange. This resulted in I-5 being shut down for several days in the southbound direction, with traffic diverting to several other routes, including SR 507 through Yelm in Thurston County. Traffic diversions from I-5 through Yelm are becoming more common, and in 2017 the City of Yelm asked TRPC to develop a traffic simulation model that could be used to show the effect of the diversions. Short videos showing traffic simulations during average conditions and during the incident are included in the presentation below.
Please note: the simulation is for planning purposes only.

Features can be modeled on a minute by minute basis, or user defined period such as the peak hour. With this greater detail in traffic simulation, the DTA also provides more detailed measures of roadway performance enhancing transportation planning and analysis.

With a close linkage to the regional model, efficient exchange of information allows for measuring the impacts of mode choice on the roadway systems performance.

DTA models are suitable for analyses involving:

  • Incidents and construction zones,
  • Active transportation and demand management strategies,
  • Integrated corridor management strategies, including traffic signal synchronization
  • Intelligent Transportation Systems (ITS), and other operational strategies
  • Capacity increasing strategies, such as new connections, intersection treatments, addition of turn lanes, or access control

Click map to enlarge

Current DTA Subarea models

  • Marvin Road area (Thurston County)
  • Downtown Olympia
  • City of Yelm (under development)
  • Grand Mound area (under development)
  • I-5 Corridor (under development)
  • Great Thurston County (under development)