The U.S. Environmental Protection Agency (EPA) developed the computer program, Motor Vehicle Emissions Simulator (MOVES), to model carbon monoxide (CO), coarse particulate matter (PM10), fine particulate matter (PM2.5), and mobile source air toxics (MSATs) emissions. The model can also perform greenhouse gas emissions analyses. Forty-nine states use MOVES while California uses EMission FACtors (EMFAC) model to estimate vehicle emissions. Project level analyses may also require the use of dispersion models such as CAL3QHC, CAL3QHCR, or AERMOD. Running these dispersion and emissions models require a high level of technical expertise. With the complexity of the models, the associated requirements/guidance, and the computer programs developed, many state departments of transportation (DOTs) are finding it technically challenging to perform air quality analysis or review analyses completed by consultants. In particular, there is a need for a user-friendly software, graphical user interface, or web-based interface for practitioners working on transportation air quality analyses at the project level. Practitioners need a combined interface to input data on a step-by-step basis, select dispersion or emission models, run the models, and process the outputs. Research is needed to create such a combined interface for running existing federally approved and public domain models. The objective of this project is to develop a combined user-friendly interface for air quality practitioners to run: (a) EPA approved public domain emission and dispersion models for carbon monoxide and particulate matter, and (b) public domain emission models for mobile source air toxics and greenhouse gases. The interface will be applied by practitioners to conduct and review project level transportation air quality analyses. Accomplishment of the project objective will require at least the following tasks: PHASE I - (1). Conduct an assessment of existing tools, interfaces, models, and current guidance to develop a knowledge base and preliminary specifications for the user interface. Prepare a technical memorandum providing (1) preliminary specifications for the interface addressing design architecture and functionality, and (2) the knowledge base that was used to prepare the specifications. The design architecture should, at a minimum, include plans for (a) desktop-based or web-based interface that is user friendly, versatile, and intuitive; (b) distribution as open-source software or other software available in the public domain (and not proprietary); (c) quality control, including alpha and beta testing; and (d) updates based on changes to emission and dispersion models. The functionality of the interface should include, but not be limited to: (a) a user-friendly, flexible, and transparent interface for practitioners to input data on a step-by-step basis, select the models, run the models, and process the outputs; (b) quality assurance tools; (c) ability to run the models in a "batch" mode; (d) standard summary report to support project level documentation; (e) embedded instructions providing context sensitive help; (f) ability to compare results from multiple model runs and provide multiple options for output processing; (g) ability to read and write data from geographic information systems (GIS)-based software; and (h) ability to read data from Computer Aided Design software. (2). Prepare a detailed plan to conduct user outreach and obtain feedback from practitioners who perform project level air quality analyses to fully develop the Task 1 preliminary specifications. Practitioners contacted could include (a) federal agency staff, (b) state DOT staff, (c) state designated air quality agencies, and (d) other stakeholders. The detailed plan should include a list of agencies to be contacted, contact selection criteria, a draft list of questions, and a description of how the outreach will be conducted. Upon National Cooperative Highway Research Program (NCHRP) review and approval of the detailed plan, conduct the outreach. (3). Based on Tasks 1 and 2, prepare an interim report. The interim report should include: (a) results from previous tasks; (b) revised specifications for the interface; (c) potential costs for maintenance including future updates; and (d) revised work plan for Phase II, including plans for alpha and beta testing, outlines for a user manual, training materials, software documentation designed to facilitate third party updates, and web-based or other training to be conducted. The specifications should include: (a) functional needs and requirements prioritized by cost and available budget and (b) design architecture. The Phase II work plan should include appropriate check points with the NCHRP. PHASE II - (4). Implement the approved Phase II plan to develop the interface. The interface developed should include all the elements identified in the Phase II plan. Conduct alpha testing of the product before delivery to the NCHRP. Additionally, develop a draft user manual and draft materials for outreach and training. (5). Conduct tests to demonstrate that using the interface and running the EPA approved models separately yield the same results. (6). Conduct beta tests of the Task 4 deliverables with a selected list of practitioners and generate a user acceptance report. Prepare a technical memorandum to summarize results of Tasks 5 and 6, including changes that will be made to the interface and user's guide based on the results.(7). Provide final project deliverables as identified in the Phase II report, including the interface, the user manual, training materials, software documentation, code, and suggested future work as appropriate. In addition, conduct web-based or other training for practitioners on the use of the interface.