A Snapshot of Travel Modeling Activities:
Atlanta Regional Commission (ARC)
Mid-Ohio Regional Planning Commission (MORPC)
North Central Texas Council of Governments (NCTCOG)
Puget Sound Regional Council (PSRC)
Sacramento Area Council of Governments (SACOG)
MPO Profiles – Columbus, Ohio Region
The Mid-Ohio Regional Planning Commission (MORPC) and the Licking County Area Transportation Study (LCATS) comprise the Columbus, Ohio MPO. The MPO covers Franklin and Delaware Counties, the City of Pickerington, Bloom and Violet Townships in Fairfield County, Etna Township and the City of Pataskala in Licking County, and the Newark/Heath urbanized area. The total population of the MORPC study area was 1.34 million in 2000.
Year 2000 employment in the region was 810,000. Major employers in the region include the State of Ohio and Ohio State University. Franklin County continues to be home to the majority of the employment and businesses in the region but is expected to see lower future growth in comparison to the other counties in the region. Delaware County is the fastest growing county in the region.
In 2004, the U.S. EPA designated the region a nonattainment area for failing to meet the minimum air quality standards for ozone established under the National Ambient Air Quality Standards (NAAQS) of the 1990 Clean Air Act Amendments (CAAA). The area is also a nonattainment area for particulate matter less than 2.5 microns in diameter (PM2.5).
Current Travel Forecasting Model Practice
Travel Forecasting Model
The MORPC region developed a state-of-the-art activity-based model in 2004. The new model is a disaggregate, tour-based model applied with the microsimulation of each individual household, person and tour. The model area is divided into 1,805 internal and 72 external zones and includes Franklin, Delaware, and Licking counties, and parts of Fairfield, Pickaway, Madison, and Union counties. The primary inputs to the model are transportation networks and zonal data, where each zone features the standard socioeconomic characteristics that would normally be found for use in a four-step travel demand model. The MORPC activity-based models differ from activity-based models in other regions in that it utilizes zonal data rather than parcel-level data. MORPC selected the level of detail for input data after considering data availability and forecasting capabilities.
Land use forecasting is performed using a Geographic Information Systems (GIS)-based allocation model developed by MORPC to allocate land uses on a quarter-mile grid. The GIS-based model uses local communities’ land use projections as input and adjusts those projections to match control totals specified by the State of Ohio. The GIS-based model considers accessibility and the availability of water and sewer resources in the allocation process. After conducting a final review of the allocations, planning staff further allocates land uses to TAZs using GIS. Staffs from local communities then review and approve the TAZ-level forecasts prior to final adoption by the MPO.
The travel demand model has been validated to traffic and transit count data, Census Transportation Planning Package (CTPP) place-of-work by place-of-residence (worker flow) tables, on-board transit survey data, data from a 1999 home interview survey data of 5,525 households, and data from the Ohio Department of Transportation (ODOT) 1995 external cordon origin-destination roadside survey.
Due to its complexity, MORPC maintains tight control over who can run the model. Currently, the model can be run by MORPC, ODOT and qualified, contracted consultants who can demonstrate a need for the entire model. For transit studies, the complete model has been provided to the (qualified) consultant. For highway studies and National Environmental Protection Act (NEPA) purposes, consultants request data (traffic projections, etc.) from MORPC or ODOT. The activity-based model has not been provided to consultants for any highway studies. When conducting initial planning studies, the basic model output is often used to screen and reduce conceptual alternatives. However, for forecasted design hour traffic volumes, the raw model output are always adjusted and refined using NCHRP 255 procedures. ODOT has developed a spreadsheet tool used to develop design volumes for projects from the model results.
Dublin, Ohio, a community within the MPO region, has developed a basic travel model for public use and for the development of its comprehensive plan. Dublin coordinated with MORPC to ensure that its model used a compatible zone structure to the MORPC model. Dublin provides land use data to MORPC and MORPC provides data from the regional model for Dublin’s external-external and internal-external trips.
Travel Forecasting Model’s Role in Transportation Planning Process
MORPC uses the travel model extensively to provide a quantitative underpinning for decision-making in the transportation planning process. This approach is in accord with the support provided by ODOT for modeling and analytic methods.
MORPC has three goals for the Long-Range Transportation Plan (TPlan): improving transportation efficiency, improving the multimodal aspect of the network, and improving the quality of life in the region. Each of these goals has associated measures which are used to help rank projects. The quantitative measures derived directly or indirectly from the model for each of the three goals are:
- Transportation Efficiency – Average 2030 peak travel delay reduction per person, improvement in both 2015 and 2030 Levels of Service (LOS) in corridors, efficiency improvement, and percentage of trucks;
- Multimodal Measures – Pedestrian connections, bicycle connections, travel demand management (TDM) measures, and service to intermodal facilities;
- Quality of Life – Equality and justice for transportation disadvantaged, air quality impacts, fuel consumption reduction, and nonretail jobs served.
In addition to the TPlan, the measures have been applied for New Starts applications, major corridor Environmental Impact Statements (EIS), and Interchange Justification Studies. The model results are used to estimate measures such as travel delay, changes in mode use, and changes in travel patterns and behavior.
The development of the TPlan starts with the collection of information from local communities regarding needed improvements. While many of the needed improvements are supported by special studies conducted for proposed projects, there is no requirement that modeling be used for the studies. Projects might also be identified via other studies such as corridor and subarea studies or regional studies used to identify transportation system deficiencies.
The next step of the process is to determine the potential projects included in the TPlan. The selection process considers the following factors:
- Listing of the project in the TIP and whether the project is past the concept stage;
- Quantitative evaluation of the project based on results from the regional travel model and GIS-based factors.
The quantitative evaluation yields a score using the measures associated with the TPlan’s goals. TPlan projects are prioritized using this score along with non-model factors such as safety considerations, impact on freight movement, ITS improvements, regional or local security concerns, general community support, and financial support.
The most recent TPlan process is the first in which funding played a major role. An estimated $22 billion in needed transportation improvements was identified for the region but funding for only $3.5 billion was available. The funding shortfall caused the project selection process for the regional transportation plan to be even more quantitative than the process used for previous plan development.
While the TPlan is directly influenced by the quantitative element of the model, the quantitative results can also be used to indirectly influence projects included in the plan. For example, model results prepared during the preliminary engineering and EIS stage recently recommended that a two-lane roadway should be widened to five lanes to handle forecast traffic. Although the project was included in the TPlan, the road went through a suburban community that opposed the road widening. Since funding for a road less than the required five lanes was not authorized, the project was not included in the next TPlan update, and did not proceed. There are no specific instances of a project being removed from the TPlan as a direct result of model results. Those decisions are made earlier in the projection identification process.
Detailed model results are used in special studies conducted prior to the TPlan selection process. Summaries of these results are then presented to the board’s special committees reviewing or overseeing the study. Projects must be supported by a study, including modeling, performed prior to consideration for the TPlan. In this way, every project under consideration has been justified through modeling, whether it is ultimately included or not. The public has responded positively to using model data to justify decisions made in the analytical process.
Support for Travel Forecasting Models
MORPC receives about $2 million per year from FHWA Metropolitan Planning (PL) funds, excluding funds for special projects. The PL funds are allocated as follows: data staffing receives about a $400,000 to $500,000 for four full-time staff; model assistance and maintenance receives about $400,000 for four staff; short-range planning, which includes multimodal planning, management and operations, and safety planning, receives about a $300,000; the TIP, including implementation, transportation data, and models, receives about $500,000; and long-range planning, including multimodal planning, public service and involvement, receives about $300,000.
Major model updates have been funded out of special studies. For the past two to three years, approximately $60,000 in additional funds has been allocated for the collection of traffic data. The activity-based model was developed using Surface Transportation Program (STP) funds as a supplement. The most recent household travel survey also was performed using STP funds.
MORPC has a close relationship with ODOT for model support. It also has an informal relationship with Ohio State University (OSU) and close ties to the engineering department. MORPC works closely with the Central Ohio Transportation Authority (COTA), the regional transit authority, and performs the modeling required for the development of COTA’s long-range plan.
Primary Challenges and Emerging Issues
The major issue faced by central Ohio is overall travel growth resulting from rapid economic expansion in the region. MORPC uses the model primarily for analysis of growth strategies and expansion of the transportation network.
Traffic operations and other congestion management strategies have not been a primary focus of travel modeling. By law, the Ohio Turnpike is the only tolled road in Ohio. Since this is not anticipated to change anytime soon, pricing has not been an issue considered by MORPC. The activity-based model includes the cost of travel (including tolls) as an explanatory variable and the traffic assignment process has the capability to include tolls through the coding of link attributes in the roadway network. Since the model includes equilibration, the resulting travel costs are fed back into the activity-based model.
MORPC does not currently model traffic operations although building these capabilities into a future version of the model is being considered. If the region was more static with respect to growth, traffic operations modeling and dynamic traffic assignment might be more of an issue due to the need to optimize existing facilities. Since the area is growing, the primary issues being considered relate to increasing capacity and adding new transportation facilities in the region. Special studies and ad hoc analyses can be used to investigate traffic operations in a particular corridor or project area.
A number of large distribution centers are moving to the Columbus area. The truck travel associated with these centers will impact travel in general and will need to be addressed in future planning. The current model has a truck component based on Quick Response Freight Manual (QRFM) methods. One improvement being considered for the activity-based model is the extraction of truck trip tables from the statewide freight model. The statewide freight model is anticipated to be completed by the end of 2008. MORPC is interested in freight modeling information, including commodity mode shifts, mode use by distance, pricing data, estimated rail system capacity with comparisons to road system freight capacity, and the impact of intermodal facilities on traffic, and through trips.
Even though MORPC does not consider congestion management strategies such as pricing as a major focus in travel modeling, its activity-based model structure does have the built-in capability to examine time-specific issues from the demand side. MORPC’s activity-based model can model travel demand for each of 15 hourly periods (from 5:30 am to 11:30 pm). Since the model includes a feedback loop into the tour generation phase of the model, trips are allowed to shift out of the peak hour(s). This modeling approach makes it possible for the agency to partially investigate time-specific issues such as parking, telecommuting, reversible lanes, and high-occupancy vehicle (HOV) lanes; time dependent issues such as changes in travel speeds and volumes; and peak spreading issues in highly congested networks. The time-of-day model, operating in conjunction with the destination choice model, allows trips to shift from the peak period to the off-peak period through the use of three global iterations of the model system. The 15 hourly periods are aggregated to four periods for assignment (AM peak, Midday, PM peak, and Night). A one hour peak within the peak period is assumed for the static equilibrium traffic assignment process. However, there is no dynamic assignment or traffic simulation process that allows peak spreading within the existing assignment process.
Uncertainty in travel forecasts is currently addressed by MORPC through the documentation of all assumptions, particularly on the land use side. Whenever traffic assignment results are distributed, traffic volumes are rounded to convey the uncertainties inherent in the numbers.
Future Plan for Travel Forecasting Model Update
Motivation for the Major Model Update
The region just recently completed the development of the activity-based travel model. The primary reason for updating the previous four-step model was the evaluation of light rail transit options for the region.
Several short-term updates to the regional model are planned, including: a validation of the model by time-of-day (most likely to the four time periods used for assignment) against observed 2005 data; network coding to the intersection level of detail (requested by ODOT for all regional travel models in Ohio); and an update of the mode choice model component of the activity-based model using data from a transit on-board survey planned for 2009.
As described above, there is a desire to improve freight and goods movement modeling for the region, and to add more operations-related modeling capabilities to the regional model, if possible. The design of an improved goods movement model and the collection of data required to estimate the model have not been thoroughly examined, and would be included in the long-range model improvement plan. One long-term model applications change being considered is the migration of the model from Java to Cube scripts. This migration will be performed by segments to evaluate and assess the impacts of differences in model run times.