Using state of the art or state of the practice methods, Modeling & Forecasting works directly with the staffs of MPOs, the planning & design divisions of state and federal agencies, and their consultants to produce traffic forecasts for transportation project and policy alternatives. Ultimately, the customers of these forecasts are agencies at all levels of government who build, operate, and maintain the transportation system, as well as the general public.
Staff Roles & Responsibilities
Staff within the work unit produces 20-25 year forecasts of traffic flows on the roadway system for roadway design. Design aspects such as number of lanes, number and length of turn lanes at intersections, interchange configurations, pavement type and thickness, and other roadway geometry depend on this certified traffic forecast. Traffic flows produced by travel demand forecasting models are used as the basis for certified traffic.
The work unit sets standards for travel demand models in Ohio working in coordination with the Ohio Travel Demand Model Users Group (OTDMUG). The work unit builds and maintains travel demand models used in Ohio. These travel demand models are used for a number of transportation planning activities beyond certified traffic for roadway design. Model results are also used to evaluate alternative roadway locations, evaluate impact and feasibility of other modes of travel such as bus and light rail, and the impact of policy decisions on the transportation system. The work unit supports urban area models used by Metropolitan Planning Organizations (MPOs) as well as a statewide model for Ohio.
In coordination with MPOs, modelers in the work unit use the travel demand model results coupled with the MOVES transportation pollution emission model produced by the Environmental Protection Agency (EPA) to perform regional emissions analysis of long range transportation plans. In addition, the work unit produces project level air toxic emissions estimates to satisfy Federal requirements and for such things as funding eligibility in support of other departmental planning activities.
Traffic Forecasting dates back to the 1930s when the Bureau of Public Roads first started the federal financing of highway projects. From the very beginning, traffic counts were collected and growth rates were applied to produce a travel demand forecast used for planning and design purposes. The purpose of traffic forecasting is to produce future estimates of average daily traffic (ADT), design hour volumes (DHV) and truck percentages (TD and T24) for use in design and planning.
The need for certified traffic forecasts was originally dictated by a directive from the FHWA and is specified in Section 102 of the Location and Design Manual. (Section 102 - Traffic Data, states, “All traffic data used shall be certified by the Office of Technical Services.”)
Certified traffic is also referenced in several key ODOT design documents as follows:
- State Highway Access Management Manual (Version 8-15-03) - (Section 5.5.5)
- Location and Design Manual (revised Oct. 2008) - (Section 102 and Section 550)
- Traffic Engineering Manual (April 17, 2009) – (Section 402-2 – Traffic Volumes)
Modeling & Forecasting develops certified traffic forecasts for projects and reviews forecasts developed by others. Traffic forecasts developed by Modeling & Forecasting utilize the methodology discussed in NCHRP 255. Certified traffic is typically requested by Central Office and District Personnel.
Travel Demand Modeling
Travel Demand Models (TDM) are used to forecast traffic flows on the transportation system. Although the transportation system may include other modes of travel such as walking, bikes, or trains, the models are typically used for evaluating roadway improvements or improvements to bus service. These models are used only for long range forecasts: 20 to 30 years. TDMs are used by consulting firms, metropolitan planning organizations (MPO), and state departments of transportation (DOT) to identify possible future year transportation system deficiencies that may not exist today. These agencies also use the models to evaluate the impacts of alternative transportation solutions for development of long range transportation plans. TDMs are used as the basis for “Certified Traffic” forecasts, for pollution emission estimates, and for congestion management system statistics.
A travel demand model is a program or set of computer programs and data which are assembled and usually run by professionals who specialize in travel forecasting. There are only a few developers that offer travel demand modeling software packages that run on personal computers. Some of the well known packages are QRSII, Cube Voyager, and TransCAD. For models used in Ohio, other programs developed by the DOT, consultants, or MPOs are also part of the model. Land use, demographic data, and regional trip characteristics for a region (typically one or more counties) are combined with this software for a single model.
The traffic forecasts are based on forecasted land use, demographics, and travel patterns unique to the region. Regions range in size from half a county to several counties. The largest models cover an entire state and include effects of growth of the economy from coast to coast.
Therefore, inputs to the models include the transportation network and variables such as population, employment, households, dwelling units, trip rates, transit fares, etc. Among other statistics and reports, outputs from the model are maps of the transportation system with traffic volumes for every roadway segment.
Contact: Greg Giaimo | Greg.Giaimo@dot.ohio.gov | 614-752-5738
Air quality conformity applies to long-range transportation plans, shorter-term transportation improvement programs (TIPs) and transportation projects funded or approved by the Federal Highway Administration (FHWA) or the Federal Transit Administration (FTA). Conformity requirements apply in areas that either do not meet or previously have not met certain air quality standards.
Conformity determinations must be made at least every three years, or when transportation plans or TIPs are updated. In addition, conformity determinations must be made within 12-months of an area being designated by Environmental Protection Agency (EPA) as nonattainment for ozone (O3), particulate matter (PM-2.5), or nitrogen oxides (NOx), the pollutants for which conformity is required.
Different regions throughout Ohio require conformity determinations, most of which lie within MPO boundaries. In these areas, the MPOs travel demand model must be used to forecast traffic that will be used in estimating future emissions due to vehicles.
Total regional emissions are calculated using the vehicle miles traveled (VMT) from the model output, and they are multiplied by emission rates (in grams/mile traveled). The emission rates are generated using the EPA’s MOVES (MOtor Vehicle Emissions Simulator) air quality model.
Another growing area of air quality involves analyses of Mobile Source Air Toxics (MSAT). Mobile source air toxics are compounds emitted from highway vehicles and non-road equipment which are known or suspected to cause cancer or other serious health and environmental effects. Emission rates for MSATs are also generated using the MOVES air quality model, and they are likewise used in conjunction with MPO travel demand models to estimate total pollutant levels.
Contact: Nino Brunello | Nino.Brunello@dot.ohio.gov | 614-752-574
The federal government, as part of the “FAST Act” authorizing spending on surface transportation, directed the FHWA to establish national performance measures for many of the goals established. This is intended to support improved investment decision making, to more efficiently meet national goals. One of the stated goals is improved system performance and the easing of congestion, to be measured via an annual update of the Level of Travel Time Reliability (LOTTR) and amount of Peak Hour Excessive Delay (PHED) for every segment on the National Highway System (NHS) where travel time data exists. These statistics (along with other data supporting performance goals for such things as safety, pavement and bridges) are a required part of the HPMS submittal all state DOTs provide to FHWA each year, and also utilized for performance reporting required of some MPO agencies.
In support of this, the modeling and forecasting section calculates the LOTTR and PHED statistics covering a full calendar year for all roadway segments on the NHS statewide following procedures recommended by FHWA. The database functionality of the TransCad software program is utilized for this, as documented in the related resources of this page. Additionally, the section produces forecast volumes and capacities needed for the annual HPMS submittal as well as volume estimates on local roadways for use in safety analysis.
Contact: Sam Granato | Sam.Granato@dot.ohio.gov | 614-644-6796