Skip to content U.S. Department of Transportation/Federal Highway AdministrationU.S. Department of Transportation/Federal Highway Administration
Office of Planning, Environment, & Realty (HEP)

Transportation Conformity Domestic Scan Report: Use of Latest Planning Assumptions and Transition to MOBILE6

Chapter 2 - Findings

Synthesis of Scan Visits

Based on the information gathered from the background materials and on-site visits, four major themes emerged: Structuring the Conformity Process; Institutional Coordination; State Commitment and Leadership; and Innovative Techniques. The scan team identified good practices and techniques that were developed to help facilitate the conformity process and, to a certain degree, the transportation planning process at these sites. A number of suggested tools were also identified and are included in Appendix D for future consideration.

  1. Structuring the Conformity and the Transportation Planning Processes

    A common theme among all the areas visited is the existence of a "structure" to facilitate the conformity process, including the use of latest planning information in the regional emissions analysis. Examples of these "structures" include: documenting data and assumptions used in the conformity process; developing coordinated timelines for various actions to ensure that conformity deadlines are met on time; preparing project descriptions and conformity reports in a standardized format to facilitate review, and providing checklists to stakeholders so that the development of conformity reports is thorough and includes all necessary documentation for approval by FHWA/FTA. Below are notable good practices for structuring the conformity process.

    1. Data documentation

      The importance of documenting data and assumptions used in transportation conformity has been cited frequently as a lesson learned over the past decade. Data documentation is vital for a number of reasons including: staff turnover in agencies requires a good record of decisions made and assumptions used; the complexities of travel demand and emissions models calls for good documentation so that a complete record of assumptions used in various model runs, for example, is kept; and, litigation on conformity-related issues has necessitated that good documentation be available to the public and the courts.

      Pre-Analysis Consensus Plan - The North Central Texas Council of Governments (NCTCOG - the Dallas-Ft. Worth MPO) prepares a pre-analysis consensus plan ( to streamline and improve the efficiency of the conformity process. The plan is a very detailed listing of all planning assumptions, sources of demographic data, models to be used in analysis, VMT adjustment factors, analysis years, control strategies, model validation process, project listing and schedules, etc. An interagency consultation meeting is held to build a consensus on the plan prior to the initiation of the conformity process.

      Model protocol used for consistency in planning assumptions - The Raleigh Area MPO (CAMPO) uses a model protocol ( to ensure that all planning assumptions are agreed to by the interagency consultation group and that a routine is in place to update assumptions on a regular basis. This helps all agencies that provide input (e.g., local governments, State DOT) to understand what data is needed, and recognizes that consistency across agencies is important. To ensure data consistency throughout the maintenance area, the Raleigh MPO also closely coordinates with the Durham MPO (and vice versa). This is because both MPOs are part of a single nonattainment area and have adjacent MPO boundaries.

      Data Consistency Among Multiple Stakeholder Agencies - The Atlanta Regional Commission (ARC), Georgia DOT, Georgia Environmental Protection Division (EPD), Metropolitan Atlanta Regional Transit Authority (MARTA), and Georgia Regional Transportation Authority (GRTA) use consistent data throughout the Atlanta region. Interagency and intra-agency relationships are the primary resources available to ensure data consistency. The agencies felt that data consistency is critical due to employee turnover and a high level of scrutiny over the ARC by environmental groups.

      Facilitating Use of Geographic Information Systems - The Nashville MPO is working to develop GIS capabilities in order to better coordinate with other counties and localities in the MPO region and to maintain updated population, employment and land use data. The MPO is coding business license data into the GIS system and has purchased GIS software for the other jurisdictions to help facilitate the use of GIS. The GIS work underway will result in good land use data being collected so that the MPO can better assess land use changes and more effectively integrate transportation and land use plans.

      Interactive GIS Map and Supporting Materials for Public Access - The ARC in Atlanta has developed an innovative GIS Interactive Map for the transportation plan and program in a hyperlink/CD format. This is a way to array information on the Regional Transportation Plan and TIP that allows projects to be searched based on their location in the region. The ARC GIS-based RTP and TIP is a major new innovation in displaying information in a user-friendly format for a major urban area. The public can view projects in any area within the region, obtain a fact sheet on the project and understand how the project fits into the neighborhood as well as the region. This is available on a multi-media CD with all ARC documents, a video on the RTP, reference material, and links to more than 100 different sites in 9 different categories with a brief description of each link.

    2. Coordinated Timeline

      Experience with transportation conformity has shown that keeping track of deadlines for updates of transportation plans, TIPs and associated transportation conformity determinations is very important. Also, as a complex analytical and institutional process, it is vital for all stakeholders and those responsible for executing part(s) of the process to know what is expected of them and when. The consequence for not meeting deadlines is significant and has caused many areas to go into a conformity lapse.

      Gantt Chart for Conformity Process - The NCTCOG prepares a Gantt chart ( that shows the critical path for all key activities in the transportation plan, TIP and SIP processes to ensure that all stakeholders understand which agency has responsibilities for various elements of the process and the schedule for review and agreement on draft materials. A mid-course SIP review schedule was recently added to the Gantt chart.

      State DOT sponsored kick-off meeting for each round of conformity - In Pennsylvania, all nonattainment and maintenance areas are on the same transportation planning cycle. PennDOT sponsors a kick-off meeting for all impacted areas prior to each round of transportation plan, TIP and conformity updates. This helps organize the MPOs, makes information available on data needs and timelines, and improves the quality and timeliness of conformity determinations.

    3. Standardized Project Descriptions and Conformity Report Format

      Project descriptions are needed for a number of reasons. These include: understanding the scope of a project to determine whether it is regionally significant, compiling project lists for inclusion in TIPs, and subsequently STIPs, and for doing cost estimates both on individual projects and the set of TIP and/or plan projects as a whole. For these reasons, a consistent and standardized format for project descriptions can be very helpful. The format of a conformity determination report can greatly assist those who need to review the conformity determination such as MPO technical and policy committees, stakeholders, and Federal agencies. In addition, a sufficient level of detail in conformity determinations is important so that questions can be answered and independent reviewers can easily understand the conformity report. This can save the MPO staff time in answering questions, explaining assumptions, or describing agreements made in interagency consultation.

      Standardized spreadsheet for project information - The Capital Area MPO (CAMPO) for the Raleigh area has developed a standardized project information spreadsheet CAMPO that helps organize all project information in an easy to access format. This spreadsheet was developed through the Conformity Improvement Process (CIP). The CIP is an initiative to evaluate the conformity process and ensure a standard agenda. The CIP identifies obstacles, develops solutions to improve the conformity process, and ensures consistency across the State. The CIP also ensures that all required aspects of the planning process pertinent to conformity are addressed through interagency consultation to avoid future complications

      Statewide timeline, consistent format, and standardized project description book - The State of Pennsylvania DOT(PennDOT) has established a uniform process for updating plans and TIPs and conducting conformity determinations including a timeline for required updates of planning assumptions, a standardized conformity reporting format and a standardized project description book ( This has improved efficiency and provides stability to the transportation planning and conformity processes.

      Detailed conformity determination reports - The Atlanta Regional Commission (ARC - the MPO in Atlanta) has a process in place to meticulously document all planning assumptions, model inputs and outputs, and SIP assumptions including background on the motor vehicle emissions budget. Each conformity determination report Commission ( includes very detailed interagency consultation meeting summaries.

    4. Conformity Checklist

      Many agencies have found that maintaining a checklist of all conformity requirements is helpful. This is another tool that assists the various parties to the conformity process to understand roles and responsibilities. It also helps reviewing agencies to know quickly whether a conformity determination is complete. The FHWA has included a checklist in its Reference Guide to Transportation Conformity and many agencies have used that checklist or modified it to suit local conditions.

      Conformity checklist - In Nashville a standard checklist for conformity MPO ( is being used with good documentation. This facilitates understanding of requirements and ensures complete conformity reports for the region.

  2. Institutional Coordination

    Good institutional coordination on transportation conformity issues is essential to a smoothly operating process. It also provides a mechanism for sharing information with stakeholders in an organized and timely way to support ongoing communication and information sharing Early and continuous institutional coordination very often enables timely detection and resolution of conformity issues such as those associated with the use of new planning information. Below are some notable examples of institutional coordination that have the areas visited have employed.

    1. Institutional Coordination

      Over the years, many studies on transportation conformity have found one common thread that appears to be a major benefit of transportation conformity, and that is improved institutional coordination. Likewise, agencies working in partnership are the most successful in a ensuring a smooth conformity process where all participants are fully informed at all steps along the way.

      Texas Technical Working Group for MOBILE6 - This group meets quarterly with the Texas Transportation Institute to discuss MOBILE6 modeling and transition issues.

      Travel demand modeling technical review team - The Tampa region has established a modeling technical team that includes the four MPOs in the Tampa area and the State DOT. Each year the group decides modeling improvement priorities for the upcoming year. Improvements have included: using household surveys to augment model inputs, goods movement surveys, analyzing external trips ("through" trips) and developing a freight model. The team meets every two to three weeks, as needed.

    2. Special Working Groups

      The benefits of forming and sharing information among special working groups, beyond the required interagency consultation process, are evident in the examples being practiced in some of the scan sites. For example, statewide working groups are helpful to ensure that all MPOs and other stakeholders stay informed of new developments, share information and techniques that can be used or replicated in other areas, and help the State DOT in the project programming (TIP) process.

      Statewide SIP Working Group - At the initiation of the FHWA Division office in Texas, the agencies in Texas have organized a statewide group to coordinate issues related to SIP development and revisions. This effort has recently been launched, with key stakeholders including the Dallas-Ft. Worth and Houston MPOs. The goal of this SIP work group is to provide better coordination and efficiency between SIP planning and development and the transportation conformity process.

      Air Quality Partners Group - In Atlanta, a group of senior management officials from stakeholder agencies was formed to ensure high-level attention to air quality issues and concerns. This in part evolved from the lawsuits in Atlanta but has helped the management officials realize the importance of good communications and a collaborative approach.

      Multi-disciplinary Technical Coordinating Committee - The West Central Florida Air Quality Coordinating Committee (WCFAQC) is comprised of approximately 30 major stakeholders including the MPOs, the state DOT and DEP, utilities, transit providers, the University of South Florida, the American Lung Association (ALA), and others. The group meets every other month and has received various grants through the MPOs to promote air quality improvements. One of the innovative programs of the WCFAQC is the Youth Environmental Associates (YEA) program at local high schools. This program is funded through a grant with the ALA and activities include a "no-drive" day for high school students, four times a year.

    3. Communications Among Partners

      Given the demands on staff in the various agencies involved in the conformity process, staff are always looking for more efficient ways to communicate. For example, E-Mail offers a good opportunity to quickly communicate on issues and to avoid the need for some travel and meetings.

      E-Mail Interagency Consultation Process - In Nashville, an E-mail consultation process is used for TIP amendments and for the discussion of projects that are exempt from conformity. In addition, a programmatic list of exempt projects ( has been developed.

  3. Strong State Commitment and Leadership

    In areas where the development and use of latest planning assumptions occurs regularly and with minimum disruption, the scan team found that there is a strong State commitment to the process and demonstrated leadership among State DOT officials to meet the conformity requirements. This includes providing the resources, both staff and funding, and technical assistance to MPOs. However, strong State leadership does not lessen the need for in-house resources within the MPOs. Further, the transfer of technical capabilities and expertise to the individual MPOs is important for establishing a transportation planning and conformity process that can effectively and address the area's mobility and air quality needs.

    1. State DOT's Commitment in Conformity Process

      State DOT leadership and commitment of resources in assisting MPOs in meeting the conformity requirements does make a difference. This is especially evident in the areas of technical assistance such as providing resources for hiring consultants or in developing a standardized transportation model. These coordinated efforts will ensure that planning assumptions used in each conformity analysis be included.

      State DOT Commitment and Leadership - The Pennsylvania Department of Transportation (PennDOT) has played a key role in ensuring that all nonattainment and maintenance areas comply with transportation planning and conformity requirements. PennDOT has contracted with a consultant to conduct the conformity determinations in all areas in the state except for the urban areas of, Pittsburgh, Allentown, Lancaster, Harrisburg and Philadelphia. Resources to fund these efforts have been provided since 1993 and the State DOT has a small staff that oversees the consultant's work. The State's goal is to gradually develop the technical capabilities at the MPO level and have the MPOs take over the conformity process. Lancaster and Harrisburg are smaller MPOs that have recently taken over the conformity process with back up and assistance from the consultant as needed.

      Mobile Source Emission Reduction Measure Handbook - Texas DOT (TXDOT) and the Texas Transportation Institute collaborated to produce this handbook which includes a proposed methodology for estimating impacts of transportation control measures (TCMs). The handbook will be published following review and comment by stakeholders.

      Technical Study Sponsored by State DOTs - Tennessee DOT is a sponsor of the Arkansas/Tennessee/Mississippi Ozone Study (ATMOS), which, in addition to studying the ozone transport issues in the region, quantifies the effect of TCM-like projects using off-model analysis.

      One Travel Demand Model Used Statewide - The Florida Standard Urban Transportation Model (FSUTM) is used statewide by the individual MPOs such as Hillsborough and Pinellas County MPOs in the Tampa area. All four counties within the maintenance area use the model, all with the same assumptions. "What if" scenarios can be tested at the MPO level and each MPO has modeling capability. Although the MPOs have the ability to modify the model, the FDOT district office is the gatekeeper for the official travel demand model files to ensure quality control.

    2. State Leadership in Facilitating Discussion and Problem Solving

      State agencies have played a key role in helping ensure that potential problems are identified early and that conformity stakeholders collaborate to resolve issues. This leadership is particularly important in States with many nonattainment or maintenance areas.

      Statewide monthly conference call - The North Carolina DOT, in coordination with the State Department of Environment and Natural Resources (NCDENR), sponsors a statewide call each month for areas subject to conformity requirements. This serves as a useful and timely way to share information and to ensure consistency within the state in addressing various conformity issues.

      Texas Statewide Air Quality Steering Group - This group, which includes businesses, elected officials, environmental groups and the Texas Commission on Environmental Quality (TCEQ), EPA, TXDOT and major MPOs discusses control strategies that TCEQ may not be able to implement on their own or without public or private sector support.

      MPO Conformity Staff - Capacity Building - The North Carolina DOT has historically been a dominant player in the transportation conformity process within the Raleigh/Durham region. Recently, the Raleigh MPO has been working to build its capacity to become a more equal partner by dedicating a new staff person to transportation conformity including handling demographic projections and modeling responsibilities. With State support, it is expected that the MPO will be able to carry-out the conformity process in the future.

      Early establishment of interagency consultation for 8-hour ozone and fine particulate matter (PM2.5) areas - In Georgia, State and Federal agencies initiated a statewide, quarterly interagency consultation process for areas that anticipate being designated nonattainment for the new 8-hour ozone and PM 2.5 air quality standards. The State agencies expect this to enable the new areas to be better informed about transportation conformity requirements so that they can meet the need to have conforming plans and TIPs in place 12-months after the effective date of nonattainment designations.

      Statewide On-line Conformity Information - In Florida, the State DOT has been instrumental in coordinating conformity issues and maintains on-line information including a conformity checklist and guidelines, ( an MPO manual, and information on the cycle for transportation plan, TIP and conformity updates. There also is a consistent statewide project numbering system and a process through E-Mail to agree on exempt projects and regionally significant projects. The State DOT commits considerable human and financial resources to these efforts and this clearly has assisted the MPOs in the conformity process.

      Annual Statewide Conformity Meeting - The Florida DOT facilitates an annual statewide conformity meeting with representatives from the Federal, State and local agencies (including all six MPOs within the three maintenance areas within Florida). FHWA-Florida Division and EPA Region 4 are very active members of the annual meeting and provide presentations aimed at facilitating conformity implementation in the State.

    3. State Initiatives

      In recent years there has been a movement throughout the country to plan more thoughtfully for growth. A number of statewide initiatives were on the ballot in 2000 and 2002 to put measures in place to provide incentives and/or require local governments to do comprehensive land use planning. These initiatives provide good opportunities for planning assumption updates.

      Statewide Land Use Statute - In 1985, the Florida State Legislature enacted a land use statute resulting in the development of comprehensive land use plans in each county and updating of the plans every five years. This "concurrency process" ensures that any development occurs in areas where infrastructure is in place to serve the development. If development is done outside the Urban Service Area (USA), the county or the developer must pay the cost of infrastructure and no State funds can be used. In the Tampa area, Pinellas County has a growth management plan with 25 local governments and Hillsborough County's plan includes three cities. Through this process, population, employment and land use data is generated and used in travel demand models. Socio-economic data are updated every three years on the schedule corresponding with the transportation plan update cycle.

  4. Innovative Techniques

    During the scan visits, numerous techniques and data sources were discussed to show how data used in the conformity process can be generated and tailored to reflect local and regional conditions. These sources of data are primarily used in the travel demand and emissions modeling processes. Some of these techniques are especially useful in addressing data issues related to MOBILE6 transition

    1. Data Sources

      Transportation conformity is largely based on an analytical process that requires data which, prior to 1990, MPOs may not have needed. One example is vehicle registration and fleet mix data which are required data for estimating emissions. Innovative data sources have emerged in some areas and help make the conformity process more robust.

      School District information - In Pennsylvania, school district information is used as an alternate source of population data and augments census block information.

      State-based Road Management System - The PennDOT Road Management System (RMS) provides data on road inventory for the state-owned portion of the road system and allows PennDOT to improve the quality of HPMS data. This source of travel data is particularly helpful for conformity efforts conducted by smaller MPO's and rural areas.

      Innovative sources and uses of data - The Capital Area MPO (CAMPO) in the Raleigh, NC area uses a number of innovative data sources for transportation and emissions modeling purposes. These include: crash data from the State Department of Motor Vehicles to determine the fraction of vehicles subject to Inspection and Maintenance Program requirements and raw data from the State DMV used to develop vehicle age profiles. In addition, CAMPO uses InfoUSA data (employment records for the region updated twice a year) in collaboration with the Chamber of Commerce which funds access to this data for the MPO. Census data is updated annually using tax/parcel map data; and speed data is used from Global Positioning System (GPS) technology placed on paratransit agency vehicles.

      Improved Truck Data - In Atlanta, a commercial vehicle survey was completed in the mid-1990s and used to develop the truck component of the travel demand model. Georgia DOT and Georgia Tech are currently conducting independent truck studies to update the truck information for the region. Georgia Tech is conducting this independent research effort on a contract provided by GRTA.

      Improved Freight and Truck Data - In Nashville, the MPO has initiated a freight movement study, which includes an assessment of the potential for diverting truck traffic to rail in the future. Tennessee DOT has completed a rail study ( that will augment this analysis.

    2. Data Collection Techniques

      Data collection is also important to MPOs and rural areas because it can help make the conformity process reflect local conditions and rely less on national default data, that may not be accurate in a given locale.

      Improved trip origin and destination data - NCTCOG conducted parking lot surveys so that they can better determine trip origin and destination information. This included recording of vehicle identification numbers (VIN) which then are tracked to vehicle registration data.

      Travel surveys every ten years - The NCTCOG conducts comprehensive travel surveys every ten years with the most recent having a budget of approximately $2 million. Information collected includes traveler behavior, household demographics, trip generators and attractors, etc.

      Truck activity by time of day by facility type - NCTCOG plans to examine detailed truck activity by time of day by facility type and possibly use GPS technology to collect this information. NCTCOG believes that this will make their heavy-duty truck information more accurate and reflect local activity for this vehicle classification.

    3. Data Analysis, Preparation and Documentation

      Good development and documentation of data is central to the regional emissions analysis. Some areas have put a major emphasis on developing data sets that reflect local conditions and on updating data on a routine basis.

      Innovative modeling enhancements - The Tampa region has several efforts underway to enhance travel data including: travel activity of students through dorm surveys and other group quarters, analyzing household data for life style differences (e.g., households with no children, elderly persons, etc.), and using travel logs.

      Documentation of data and inputs - NCTCOG has a process in place to diligently document all modeling data inputs along with justification for use of each. This is intended to assist in protecting the agency should there be legal challenges and to provide a historical record of which assumptions have been used in conformity determinations.

      Improvements to accuracy in VMT estimates - The NCTCOG in Dallas-Ft. Worth is working to improve the quality of VMT data by incorporating alternative sources such as saturation counts conducted by TX DOT, into the VMT estimates used in modeling. Members of the interagency consultation group agreed with this approach contingent upon NCTCOG's agreement to continue using these alternative sources of data in the future.

      Uniformity in Travel Demand Modeling - The ARC in Atlanta developed TP+ modeling protocols in order to ensure uniformity in use of the travel demand model by different agencies. TRANSCAD is used for off-model analysis.

      TRANSCAD Internal Peer Review - NCTCOG has an internal peer review group to work on the transition to TRANSCAD. This aids the MPO in working through issues and building consensus within the organization about inputs, sensitivities, and other transition issues.

      Speed Studies - GRTA, in conjunction with ARC, EPD and GDOT, conducted two speed studies to update free flow speeds by facility type/area and to develop improved volume-delay curves by facility type/area and time of day. These studies were segment based and enable the development of link-by-link and point-to-point speeds in the region for four time periods during the day.

    4. Transition to MOBILE6

      The transition to MOBILE6 has been a focus of many MPOs over the past two years, given that all conformity analysis started after January 29, 2004, the end of the grace period, must be based on MOBILE6. While the transition is in different stages in different areas, much progress has been made in gearing up for use of the new model.

      Agreement on MOBILE6 Assumptions and Schedule for SIP Revision - In Atlanta, the interagency consultation group has agreed upon the MOBILE6 assumptions to be used and the Environmental Protection Department (EPD) is working to update the SIP using MOBILE6 prior to the next conformity determination.

      Use of MOBILE6 for Maintenance Plan Update - In Tampa the recently submitted updated to the maintenance plan was done using MOBILE6. Default data for vehicle age and registration and speeds was used because the region does not have other available data.

      MOBILE6 for Mid-Course SIP Review - The NCTCOG in Dallas-Ft. Worth is coordinating the schedule for the update of the plan and TIP with the Texas Commission on Environmental Quality (TCEQ) to ensure that the SIP is revised prior to use of MOBILE6 for the next conformity determination. The region is planning to do one more conformity determination with MOBILE5 before the expiration of the MOBILE6 grace period.

      Incremental Development of Local Inputs to MOBILE6 - In Pennsylvania, there are plans to incrementally develop local data inputs for MOBILE6 based upon the highest pay-off inputs in terms of sensitivities to local vs. national default data. The most sensitive inputs are speeds and vehicle miles traveled.

      MOBILE6 Sensitivity Analysis - The NCTCOG in Dallas-Ft. Worth is conducting sensitivity analysis to determine whether local data or national defaults should be used for various MOBILE6 assumptions. Planned areas of analysis include: identifying which inputs effect emissions rates and identifying those inputs which account for a high proportion of emissions (e.g. heavy-duty diesel) and focus on collecting local data for those vehicle classifications. NCTCOG is also testing absolute humidity for 15 different time periods and temperatures to better reflect local temperatures and traffic conditions.

      Accounting for non-recurring congestion - NCTCOG is accounting for non-recurring congestion in the emissions inventory so that they can take credit for strategies that reduce emissions due to non-recurring congestion (e.g., ITS improvements).

      VMT Profiles from Travel Model Data - The PennDOT contractor prepares MOBILE6 input files of VMT profiles (VMT by hour, speed range, and facility) in an automated process that extracts the information from the travel model.

Updated: 10/20/2015
HEP Home Planning Environment Real Estate
Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000
Turner-Fairbank Highway Research Center | 6300 Georgetown Pike | McLean, VA | 22101