On-road Traffic Operation Data Aligned with Model Validation Need for Project-Level PM2.5 Conformity Analysis
Research Idea Scope
When applying MOVES (MOtor Vehicle Emission Simulator) in project-level PM (particulate matter) conformity analysis, link-based traffic characteristics are required at local on-road level so as to ensure realistically representation of the local scale air quality modeling assessments. Fractions of the link traffic volume and average speed are represented by each vehicle type, which is defined as an emission source type in MOVES. Heavy truck traffic has been recognized one of the major sources of PM emissions (PM2.5 or PM10), and on-road traffic related emission varies with traffic operation conditions (e.g., speed, acceleration or deceleration) and fleet compositions (i.e., percentage of vehicle types in traffic streams). Operating mode distribution is one of critical variables representing the attribute of a link traffic activity. The US Environmental Protection Agency (EPA) recommends obtaining the data from either other locations with similar geometric and traffic characteristics, or output from micro-simulation models. However, locally acquiring accurate fleet composition and relevant traffic operation data is always a challenge at various categories of roadways. And little practical experiences are reported on MOVES model calibration and validation of the link-based emission factors. No outcomes from traffic simulation models are viewed reliable unless passing the calibration and validation tests.
The goal of the proposed research is two-fold: 1) to explore suitability of traffic data sources and data collection techniques to be compatible with the local traffic data need for project-level PM2.5 conformity analysis; and 2) provide a proof-of-concept study on model validation for conformity analysis to MOVES and microscopic traffic simulation models in an integrated way. The following two research activities are proposed:
- Investigate traffic data sources and collection techniques applied in numerous states in US for various categories of roadways. Two major types of data courses will be investigated: data sources for generating inputs for the project-level FM2.5 conformity, and data sources and techniques for generating required data for applications of MOVES and traffic simulation models in conformity analysis. Major traffic flow characteristics, such as traffic flow speed, vehicle classification, acceleration/deceleration, and road slop as well, are required to be obtained simultaneously for concerned periods of time. Data collection techniques that are commonly used in states will be investigated and identified to be suitable for the conformity analysis. The techniques may include manual, portable (road tube), loop, video detection, and permanent Automatic Traffic Recorders (ATR), and intelligent transportation systems (ITS) methods.
- Develop model validation procedure in applying MOVES along with microscopic traffic simulation for project-level conformity analysis using local link-based on-road data to improve the accuracy of local scale air quality modeling assessments. A case study will be conducted at a typical freeway, arterial, and a local street, all of which are located in a nonattainment and maintenance (N&M) area. The PM2.5 N&M areas are identified through evaluating regional level data acquired at a local metropolitan planning organization (MPO) and county environmental service agency. The data will be carefully evaluated against National Ambient Air Quality Standards (NAAQS). Traffic data and PM2.5 as well as meteorological data will be collected simultaneously at the study site. Proper design of applying the identified traffic data collection technique and/or data sources will be involved in this activity. The gained data will be used for studying the calibration and validation procedure of both models (no standard procedure is currently available for MOVES). Criteria for applying the identified data source as input of link-based traffic activities will be verified and/or recommended for update.
- Evaluate regional-level and project-level MOVES input variables for conformity analysis to recommend possible changes that should be made to regional MOVES input criteria for use in the development of project-level MOVES analysis; identify new inputs for project level MOVES analysis that are currently not used; and identify traffic activity and/or operation related criteria for requiring hot-spot analysis.
Urgency and Payoff
The research result will better clarify the localized data barrier in project-level PM2.5 conformity analysis and provide a solution to proof-of-concept framework for a solution by taking advantage of the existing traffic data sources and collection techniques. More significantly, a proof-of-concept procedure for validating MOVES and traffic simulation models in an integrated manner will be provided to facilitate the application of the involved traffic and emission related models in the project-level conformity analysis. Convincible model validation procedure is a key factor to ensure the reliability and quality control of conformity analysis when MOVES and traffic simulation models are applied. Finally, recommendation about utilizing regional level data as part of project-level analysis will be expected to maximize the data source at MPOs or county environmental services while reducing the data collection burden at the microscopic level.
Heng Wei, University of Cincinnati