Dynamic, Integrated Model System: Sacramento-Area Application, Volume 1: Summary Report (2014)

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13 Introduction: Project Overview and Objectives The second Strategic Highway Research Program (SHRP 2) Project C10B, Partnership to Develop an Integrated, Advanced Travel Demand Model with Fine-Grained, Time-Sensitive Networks: Sacramento-Area Application, is an important step in the evolution of travel modeling from an aggregate, trip-based approach to a completely dynamic, disaggregate methodology. In this project, an existing disaggregate activity-based model was integrated with an existing traffic simulation model to create a new, completely disaggregate model. Both models were implemented using open-source software. At the same time that travel demand models have been evolving, traffic simulation models—which simulate the movements of vehicles through a highway network—have become more sophisticated due to improvements in com- puting. The product of SHRP 2 Project C10B is an inte- grated model that simulates individuals’ activity patterns and travel and their vehicle and transit trips as they move on a real-time basis through the transportation system. It pro- duces a true regional simulation of the travel within a region, for the first time using individually simulated travel patterns as input rather than aggregate trip tables to which temporal and spatial distributions have been applied to cre- ate synthetic patterns. A unique feature of this model is the simulation of transit vehicles as well as individual person tours using transit. The new integrated model has been developed and imple- mented for the entire Sacramento, California, region. The integrated model components include (1) SACSIM, the regional travel model maintained by the Sacramento Area Council of Governments (SACOG), the regional metropoli- tan planning organization (MPO), and (2) DynusT, a meso- scopic traffic simulation model developed by the University of Arizona. SACSIM includes an activity-based demand model, DaySim. The transit simulation is performed by FAST-TrIPs, also developed by the University of Arizona. The integrated model also includes the ability to run MOVES, the air-quality analysis program developed by the U.S. Environ- mental Protection Agency (EPA). While the C10B integrated model produces reasonable results for regional travel patterns and behavior, the true value of the model is its ability to provide analysis results that demon- strate sensitivity to policy variables more accurately than mod- els that use aggregate demand or assignment procedures. This sensitivity was tested through a series of policy and project tests conducted by SACOG, using the new integrated model and the existing SACSIM model with aggregate assignment. The SHRP 2 C10B project is documented in a series of four reports: • Dynamic, Integrated Model System: Sacramento-Area Application. Volume 1: Summary Report; • Dynamic, Integrated Model System: Sacramental-Area Application. Volume 2: Network Report; • Start-up Guide for the Dynamic, Integrated Model System: Sacramento-Area Application; and • Network Users Guide for the Dynamic, Integrated Model Sys- tem: Sacramento-Area Application. This report, the first in the series, describes the develop- ment, implementation, and testing of the integrated model. Modeling Approach To meet the objective of addressing key policy and investment questions by implementing an integrated, advanced travel demand model with a fine-grained, time-dependent network, the ideal approach is to combine the capabilities of an activity- based travel demand model with a traffic simulation model, adding enhancements to achieve goals such as the consideration of reliability in travel choices. Furthermore, to ensure success, it is essential to test this model in a “typical” metropolitan area that is large enough to encompass the necessary characteristics. Those characteristics include significant traffic congestion, a C H A P T E R 1

14 good-sized transit system, the need to perform air-quality con- formity analysis, and a growing population to test the model for forecasting. However, the area should not be so large that the resources required for model development and testing and model execution times would jeopardize the project schedule and resources. Project C10B implemented this approach by using the SACSIM travel demand model for the Sacramento area, which includes the original DaySim activity-based model, with the DynusT mesoscopic traffic microsimulation model. The integrated model was tested in the Sacramento metro- politan area, which is the 27th largest in the United States and has all of the desirable characteristics for testing the new model. The Sacramento area is growing rapidly and has a population just over 2 million. It is one of 35 U.S. metropolitan areas with a population between 1 million and 3 million and therefore similar in size to many metropolitan areas. The Sacramento Area Council of Governments (SACOG) served as the public agency partner for this project. SACOG is the designated MPO for the metropolitan area and is respon- sible for all transportation planning in the region. As the des- ignated MPO, SACOG is responsible for implementing the region’s air-quality conformity analysis required by the EPA. The California Department of Transportation (Caltrans) sup- ported SACOG’s participation in the C10B project. The components of the integrated model developed in the SHRP 2 C10B project include SACSIM, DynusT, FAST-TrIPs, and MOVES. These components are summarized in the follow- ing subsections and described in detail in Chapter 2. SACSIM SACSIM is a complete travel demand model that SACOG uses for planning in the Sacramento region. The demand for personal travel within the region is modeled by DaySim, an activity-based demand model. DaySim incorporates a variety of model features, including • The ability to model each person in the Sacramento region separately through the use of a population synthesizer that creates a synthetic population representing each person and household in the region; • The ability to model the complete daily activity pattern for each individual, including the number and sequencing of activities defined by seven purposes; • A series of logit destination, mode, and time-of-day choice models at the tour and trip levels to simulate the choices for each individual; • Estimation of the start and end times of all activities and trips to the half-hour level of resolution; and • Parcel-level spatial resolution for home and activity locations. Other components of SACSIM are used to model, at an aggregate level, the remaining components of regional travel— including travel into, out of, and through the region (external travel); truck travel; and travel to and from Sacramento Inter- national Airport. DynusT DynusT is a traffic simulation model that is used in a number of areas and lends itself well to integration with both SACSIM and MOVES. DynusT is a true disaggregate simulation model that can track individual vehicles and transit travelers through the network—consistent with tracking traveler activities in a travel demand model. Furthermore, DynusT is a true dynamic traffic assignment (DTA) model that takes into account both the spatial and temporal effects of conges- tion. Travelers departing at different times are assigned to routes calculated on the basis of the traveler’s actual experi- enced travel time, which is a critical capability for establishing a consistent and reliable traffic assignment outcome. FAST-TrIPs The Flexible Assignment and Simulation Tool for Transit and Intermodal Passengers (FAST-TrIPs) is a model that assigns transit passengers within the transportation network and loads those passengers in a dynamic (time-sensitive) simula- tion of actual travel. This system essentially serves as a plug-in to DynusT but is precompiled with DynusT and runs with the DynusT executable. FAST-TrIPs is a regionwide dynamic transit assignment model that determines an individual-specific transit route for each transit traveler in the system; it takes into account pub- lished transit schedules and transit vehicle run times that are congestion responsive and are provided by the traffic simula- tion component of DynusT. FAST-TrIPs deals with both tran- sit-only and park-and-ride trips and is able to maintain multiple constraints associated with activity time-windows and the choice of modes in multimodal travel tours. MOVES The Motor Vehicle Emission Simulator (MOVES) is the next generation mobile source emission model developed by the EPA. MOVES serves as a single comprehensive system for estimating emissions from both on-road and nonroad mobile sources. It replaces EPA’s MOBILE model as the approved model for state implementation plans (SIP) and regional or project-level transportation conformity analyses. MOVES is designed to estimate emissions at scales ranging from indi- vidual roads and intersections to large regions. The MOVES design represents a significant break from the MOBILE and

15 EMFAC (the California air-quality analysis program that measures emission factors) design: MOVES is a database- driven model—inputs, outputs, default activities, base modal emission rates, and all intermediate calculation data are stored and managed in MySQL database. MOVES model functions query and manipulate MySQL data pursuant to scenario parameters specified in a graphical user interface (GUI). This design also provides users with flexibility in con- structing and storing their own database under the unified framework in MySQL. MOVES incorporates input data that include vehicle fleet composition, traffic activities, and mete- orology parameters at the macro-, meso-, or microscale and conducts modal-based emissions calculations using a set of model functions. The outputs of emissions inventories or emissions factors are functions of modal-based vehicle emis- sion rates and detailed vehicle activities specified for the desired geographic scale. Compared with EMFAC and MOBILE (the currently approved on-road motor vehicle emission models used in California and the rest of the United States, respectively), the MOVES model represents a fundamental shift in the method- ology used to estimate on-road vehicle emissions. EMFAC and MOBILE generally derive their emissions estimates from trip- based travel activities (e.g., vehicle-miles traveled, or VMT, during a time period); they link gram per mile emissions rates to average speeds by vehicle types and technologies, taking into consideration model years and vehicle deterioration over time. MOVES, in contrast, is a modal emissions model. Emission rates in MOVES are calculated based on vehicle-specific power (VSP) that is derived from second-by-second vehicle perfor- mance characteristics for various driving modes (e.g., cruise and acceleration). VSP—a measure of the power demand placed on a vehicle under various driving modes (speed and acceleration)—has been shown to have a better correlation with emissions than trip-based average vehicle speeds. The modal nature of the MOVES emission rates allows the model to, in principle, more accurately estimate emissions at analysis scales ranging from those associated with individual transpor- tation projects to large regional emission inventories. Some objectives of C10B required revisions to the capabili- ties of the existing models. These revisions, which are described in Chapter 2, include the ability to analyze the effects of reli- ability and the use of distributed values of time, important for the analysis of road pricing. Software Approach The software architecture for the integrated model allows users to access the modeling software using a web browser, with the major model components running on one or more shared servers. This allows for the efficient sharing of large data files, alleviates the need for every modeler to have a pow- erful desktop computer, and enables analysts to use parallel processing or other techniques as necessary to ensure ade- quate performance. The software architecture is efficient, modular, and maintainable and reduces the risk of changes to one model component affecting the operation of the model as a whole. The software was developed using an iterative, incremental methodology that reduces risk, ensures continuous testing, and makes progress more transparent and predictable. The development approach has made virtually the entire suite of C10B products available to the transportation community. SACSIM and DynusT are available under open-source licenses, and the National Academy of Sciences (NAS) is the owner of all new software. While the tests of the model described in Chapter 4 used some input data from SACSIM that were developed using a proprietary modeling software package licensed to SACOG and Cambridge Systematics, Inc., the operation of the integrated model does not require any com- mercial travel demand modeling or simulation software. More details on the project software are presented in Chapter 3. The software to run SACSIM is documented by Bowman and Bradley (2006). DynusT user documentation is available at www.dynust.net. Documentation of DynusT as used in the C10B integrated model is provided in the companion report to this report, Dynamic, Integrated Model System: Sacramento-Area Application. Volume 2: Network Report (Chiu et al. 2014). Report Organization This report is structured as follows. After this introductory chapter, Chapter 2 discusses the development of the inte- grated model and its components. Chapter 3 describes the implementation of the model. Chapter 4 presents informa- tion about the testing of the new integrated model. And Chapter 5 provides conclusions for the project and directions for further research.