Ohio Traffic Forecasting Manual Module 3: Travel Demand Modeling - PowerPoint Presentation

Ohio Traffic Forecasting Manual Module 3: Travel Demand Modeling

Training Organization Ohio Traffic Forecasting Manual Ohio Traffic Forecasting Training Modules Module 1: Traffic Forecasting Background Policy, Administrative and Technical Overview      Module 2: Traffic Forecasting MethodologiesData and Parameters, Step-by-Step Procedures, Examples    Module 3: Travel Demand Forecast Modeling Model Selection, Checks and Refinements     Intended Audience Forecast User Traffic Forecaster/Modeler

Who Should Be Here? Modelers Who Will Run Models for Projects Should Already Know How to Run Ohio Cube Based Travel Demand Forecasting Models This Class Will Not Teach You How They Work or How to Run Them Forecasters Who Will Use Model Results to Create Forecasts This Class Only Covers Key Inputs and Outputs of Models Necessary for Project ForecastsIt Also Discusses the Various Early Coordination Issues Needed to Create Relevant ModelingOhio Traffic Forecasting Manual

Outline – Part I Role of Travel Demand Forecast Models What are models? Project Planning versus General Planning Types of Forecasts Modeling DecisionsModeling WorkflowOhio Traffic Forecasting Manual

Documentation and Coordination Throughout this training, the following symbols indicate: Items that are required or suggested for documentation Items that are required or suggested for coordination with ODOT M&F Ohio Traffic Forecasting Manual

Role of Travel Demand Forecast Models

What are Models? Travel Demand Forecast Models are used to aid in the production of traffic forecasts. Raw model outputs are not used directly as project level forecasts and should not be used for analysis. Ohio Traffic Forecasting Manual

What are Models? “Models”, for the purposes of this training, generally refer to regional travel demand forecasting (TDF) models and are based on: The traditional four step paradigm of Trip Generation, Trip Distribution, Mode Choice, and Traffic Assignment. Activity Based (ABM) or Tour Based models. Software includes Cube, Transcad, QRSII, etc. Ohio Traffic Forecasting Manual

What are Models? Models do not include operational traffic analysis from programs such as Corsim , VISSIM, or Synchro. However, the two must sometimes interact for project level forecasting as described later. Ohio Traffic Forecasting Manual

Ohio Models Statewide Model Urban Area Models (17) Ohio Traffic Forecasting Manual Less detailed, but more focus on freight and commercial vehicles

Ohio Models In Ohio, each of the 17 MPOs has an urban area model which focuses on passenger transport. These urban models tend to be more detailed and are used for projects completely contained in an urban area, when truck/freight travel is not the main focus . Ohio Traffic Forecasting Manual

What Are Models? A Model of Record exists for each of these. This is the default model run for each area consisting of three or four actual model runs: Base Year Validation Run“Existing” Year Model Run (optional)Long Range Plan Year - No Build Run (E+C/TIP) Long Range Plan Year - Build RunThe Model of Record is the starting point for project level modeling and is sometimes referred to directly.Ohio Traffic Forecasting Manual

Project Planning versus General Planning The distinction between project planning and general planning should be kept in mind: General Planning tends to focus on a broad area. Project Planning focuses on a specific area.Ohio Traffic Forecasting Manual

Project Planning versus General Planning Models were originally designed for General Planning tasks: Needs Analysis Long Range Plan Alternatives AnalysisAir Quality ConformityCongestion ManagementThey are calibrated to a regional level to provide reasonable daily (or multi-hour period) system statistics for these purposes.Ohio Traffic Forecasting Manual

Project Planning versus General Planning Use of models to estimate traffic volumes for individual projects requires location-specific and time-specific accuracy. The level of additional work required to produce this accuracy depends on the stage of project development. Ohio Traffic Forecasting Manual

Types of Forecasts Ohio Traffic Forecasting Manual

Types of Forecasts Raw Model Output is not subjected to any of the checking/adjusting/refining procedures. Should never be used directly as project level forecasts and should not be used for analysis.Usually comes from the Model of Record.Sometimes used in conjunction with other information to determine growth rates for smaller projects.Ohio Traffic Forecasting Manual

Types of Forecasts Planning Level Traffic has been subjected to various checks and adjustments described in this training. Not refined enough to produce reasonable values at all locations and times. Designed to answer questions on order of magnitude, such as addition of general purpose lanes. Generally only available as daily roadway segment volumes.Major projects requiring modeling will have PLT as part of the design traffic process whether requested or not.Requesting PLT to narrow alternatives saves time and resources.Ohio Traffic Forecasting Manual

Types of Forecasts Refined Alternative Level Traffic has been refined using matrix estimation or other techniques. Suitable for use in operational level models such as Synchro or TransModeler .Results can be delivered both as turning movement volumes and point origins/destinations.Less manual refinement than design traffic but still a lot of work, only done when wide area traffic simulation needed.Ohio Traffic Forecasting Manual

Types of Forecasts Design Traffic consists of the final traffic forecasts. Forecasts that have undergone the post-processing described in Volume 2. Includes turn volumes, direction factors, truck fractions, and 30 th highest hour factors.Ohio Traffic Forecasting Manual

Planning Phase During this phase, the techniques described in this training should be employed to improve the model’s operation in the project area. Ohio Traffic Forecasting Manual Develop Planning Level Traffic and potentially Design Traffic for No Build condition

Preliminary Engineering Phase Can consist of two sub-phases: Feasibility Study (formerly known as Analysis of Conceptual Alternatives) to narrow alternatives to feasible alternatives. Alternatives Evaluation Report to create a preferred alternative.Ohio Traffic Forecasting Manual

Feasibility Study At this stage, the alternatives identified in the planning phase are evaluated and compared, narrowing them down significantly. Ohio Traffic Forecasting Manual Develop Planning Level Traffic for Build alternative(s), may also create Design Traffic for Some

Feasibility Study According to the ODOT Location and Design Manual, the differences between alternatives at this stage will typically involve things like: Designation of 1000’-2000’ corridors Interchange locations Typical sections (i.e. number of lanes) These items are within the accuracy tolerance of a well-calibrated model.Therefore, Planning Level Traffic can often be used for this stage of project development.Ohio Traffic Forecasting Manual

Feasibility Study Sometimes, however, the differentiation of alternatives or the constrained nature of the study area will require more precise definition of the conceptual alternatives (e.g. turn lanes, auxiliary lanes, signal locations, ramp configurations, etc.). In these cases, even a well-calibrated model will often contain more error than the differences between alternatives. Consideration must be given to obtaining Design Traffic at this stage or developing Refined Alternative Level Traffic.Ohio Traffic Forecasting Manual

Alternative Evaluation Report Larger projects may further reduce several feasible alternatives to a single preferred alternative at this stage. Additional detail is usually needed, thus requiring Design Traffic at this stage or developing Refined Alternative Level Traffic.Ohio Traffic Forecasting Manual Develop Refined Alternative Level Traffic or Design Traffic if not already done

PDP Paths Ohio Traffic Forecasting Manual Paths 1 & 2 Paths 4 & 5 Simple transportation improvement projects that do not significantly change the highway network Routine maintenance ResurfacingMinor wideningCulvert replacementChanging an interchange typeRelocating ramp terminalsTurn lanes additions and/or modificationsTwo way left turn lanesAuxiliary freeway lanesChanging lane use A new interchangeInterchange access modificationAddition of continuous through lanes (freeway or local) in an urban or developing regionAll Complex Path 3 projectsComplex transportation improvement projects which include roadway and structure work that adds capacityModerate roadway and/or structure work that may include capacity additionsPath 3 Low Risk ProjectsNo Model WorkHigh Risk ProjectsModel Work Required

Modeling Decisions

Modeling Agreements Decisions to be made include: Type of traffic to be generated (planning level, design, etc.) Model to be used Entity to do it Time frame to do itData NeedsOutput NeedsAnalysis YearsLand Use AssumptionsDefinition of “No Build” ConditionPrevious studies or existing forecasts nearby Ohio Traffic Forecasting ManualDetermined at Early Coordination Meeting

Who Does the Modeling? ODOT Statewide Planning & Research provides model support as a service. MPO has primary responsibility in their area but can request our help. ODOT Districts are encouraged to route model work through MPO. When OSPR is involved on project modeling, we recommend early involvement to ensure models and data are ready. Ohio Traffic Forecasting Manual

Time Frame The turn around time for model work depends on various factors such as: Who does the model work (ODOT, MPO, Consultant etc.) Data availability Other priorities Magnitude of the project and analysesOhio Traffic Forecasting Manual

Model Time Frame for ODOT OSPR General Guidelines: 3 weeks to prepare model for standard major project 2 months to prepare model for complex major project 2 weeks + 1 day per alternative to model alternatives on standard major project 2 weeks + 2 days per alternative to model alternatives on complex major projects2 months to collect necessary traffic counts and dataMost of this time is related to work flow management; can provide expedited turn around time when necessary.Ohio Traffic Forecasting Manual

Data/Output Needs The need to collect data, such as counts, is one of the major determinants of turn around time and will be established during Early Coordination Meeting . Likewise, output needs should be determined early. For example, the need to provide hourly turn movements instead of daily link volumes completely changes the approach to the project. Ohio Traffic Forecasting Manual

Analysis Years Understand the difference between: Model base year Current/Project Count year Project opening year Model run near opening yearProject design yearModel run design yearHow to reconcile.Ohio Traffic Forecasting Manual

Land Use/No Build Definitions The MPO Model of Record land use variables are typically used. For traffic impact studies, must know if the proposed development is in those land use variables or not. Ohio Traffic Forecasting Manual It’s important to understand what development is modeled where.

Land Use/No Build Definitions Also important to know what if any other projects are included in the “No Build” scenarios for the project: existing networks?, LRP E+C?, LRP Build?, hybrid? Ohio Traffic Forecasting Manual

Modeling Workflow

Modeling Steps Ohio Traffic Forecasting Manual Matrix Estimation (as needed)

Define Study Area A study area should at a minimum include the following parts of the network: The next parallel facility to either side of the project facility. Two intersections or interchanges before and after the last one impacted by the project and one beyond the parallel facilities on cross routes. All of the remaining network facilities connected to and bounded by these. Traffic analysis study area is not always the same as the project study area. Consider wider impacts to traffic. Ohio Traffic Forecasting Manual

Define Study Area For complex model projects , a preliminary traffic assignment using the alternative that is likely to produce the greatest impact can be compared to the base case to determine links with “significant impact”. Significant impact could define links with more than 10% change in traffic volumes. Ohio Traffic Forecasting Manual

Model Selection The first consideration in selecting a model for use in the analysis of a project is whether or not that model is actually sensitive to the projects and policies envisioned as potential alternatives. Some models are limited in their ability to deal with: Minor operational changesTransit system changesChanges in land developmentFreight system changesTransportation demand managementTollsManaged lanesITS Ohio Traffic Forecasting Manual

Model Selection If the project and impacts lie entirely within an MPO, the MPO model will typically be used. Otherwise the statewide model will typically be used. Determination of the appropriate model to be used will be decided at the Early Coordination Meeting .Ohio Traffic Forecasting Manual

Model Checking/Refining/Adjusting Model Checking is the process of comparing model results to base conditions and model trends to independently estimated trends to determine suitability for use. Model Refining includes correcting errors in the network and zonal data discovered during model checking and adding additional detail to the model. Model Adjusting is the process of changing the model to produce better results.Ohio Traffic Forecasting Manual Documentation of this process is VERY important!

Previous Studies & Forecasts Consistency with previous studies and forecasts for the project or overlapping/abutting the project should be considered. When new results are inconsistent, a reason why should be readily available. Ohio Traffic Forecasting Manual

Volume Reporting When possible, model volumes are not reported directly. Report growth rates or differences Apply NCHRP 255/765 adjustments to produce reported volumes When they are reported directly, it is a good idea to round the results to the nearest 10, 100 or even 1000 to emphasize the imprecise nature of the results. Ohio Traffic Forecasting Manual

Model Versioning Establishing a model versioning system and recording that information with project modeling documentation makes it easier to trace back or replicate later Consider the following aspects: Version of vendors software (such as Cube 6.0) Version of the particular MPO model (OMS10 model) Source model data sets/validation version (MORPC 2010 validation, 2017 update to 2040 LRP)Ohio Traffic Forecasting Manual

Documentation Documentation of model work should include these items: Why was the work conducted How was it conducted so another person could replicate (include source data locations and model versions, use Cube Scenario Manager catalog files to define model runs and refer to them in documentation )Show the results requestedOhio Traffic Forecasting Manual