SWUTC Research Project Description

Title of Project:  An Evaluation of Mobile Source Greenhouse Gas Modeling Approaches for Traffic Management Assessment

Project Number:  161040

Principal Investigator:
Lei Yu
(713) 313-7282
P.I. Affiliation:  Texas Southern University

Project Monitor:
Mike Dio
Clean Air Technologies International, Inc.
(716) 893-5800

Project Status:  Active

Date Started:  9/1/09

Estimation Completion Date:  8/31/10

Estimated Cost - Current Fiscal:  $62,500

Estimated Cost - Total Planned:  $62,500

Project Summary:
Project Abstract:
Traffic management strategies regulate vehicle operating characteristics by affecting vehicle miles traveled (VMT), level of traffic congestion, fluctuation of speed, delay and stops at intersections, and traffic signal control strategies.  All of these factors have significant impacts on mobile source greenhouse gas (GHG) emissions.  In the past years, although extensive efforts have been made to examine traffic management strategies from the perspective of their impacts on GHG emissions, current practices still face several obstacles arising from real-world data constrains, limitations associated with the current GHG modeling approaches, and lack of systematic analysis of GHG emission reduction methodologies.  Traditional emission data collection methods are unable to capture vehicles’ real-world emission characteristics. Most of current GHG emissions modeling approaches that facilitate GHG impact assessment are insufficient to conduct the analysis necessary to address GHG emissions at project, local, or regional level.  Because there are still no regulations addressing GHG emissions from transportation sources (except California), most transportation agencies do not have enough experience in analyzing impacts of traffic management strategies on GHG emissions.

In this context, the proposed research is intended to achieve two primary objectives.  The first objective is to develop a mobile source GHG modeling approach based on Vehicle Specific Power (VSP).  Second-by-second real-world emission data under various driving patterns will be collected using Portable Emission Measurement System (PEMS) and a comprehensive GHG emission database will be established including vehicle information, real-world GHG emission data, and fuel consumption data.  Case studies will be conducted in Houston for this purpose.  The effectiveness of the proposed modeling approach will be evaluated by comparing the amount of GHG emissions generated from different modeling approaches and real-world data analysis.  The second objective is to develop evaluation approaches for traffic management strategies in terms of GHG emission control.  Comparative analysis on the amount of GHG emissions produced at different levels before and after the implementation of each traffic management strategy will be conduced.  The results from this research will promote the current practice of mobile source GHG emission measurement and GHG emission reduction related traffic management assessment, and therefore are of important practical values to the efforts of GHG emission control.

Project Objectives:
The goal of this research is to develop novel evaluation methods for traffic management strategies in terms of GHG emission control by establishing the linkage between traffic management, vehicle operating characteristics, and GHG emissions. The city of Houston is selected for the case study.    Second-by-second real-world emission data under various driving patterns will be collected using Portable Emission Measurement System (PEMS) and a comprehensive GHG emission database will be established.  The research goal is to be achieved by fulfilling the following specific objectives:

• Build up connections between GHG emissions and traffic management by quantifying GHG emissions under different vehicle operating characteristics;
• Build up a comprehensive GHG emissions database including vehicle information data, real-world GHG emission data, and fuel consumption data by colleting real-world vehicle emission data using PEMS;
• Develop a GHG emission modeling approach that is able to best reflect GHG emissions under various real-world vehicle operational conditions by incorporating Vehicle Specific Power (VSP) distributions;
• Evaluate existing and proposed mobile source GHG modeling approaches on the traffic management assessment by comparing the modeling results with real-world data analysis results; and
• Develop evaluation methods on traffic management strategies in terms of GHG emission control by comparing the amount of GHG emissions generated before and after the implementation of specific traffic management strategies.

Task Descriptions:
Task 1: Conduct Literature Review, Synthesize the Previous Studies, and Identify Research Needs
The purpose of this task is to conduct a thorough review of literatures on mobile source GHG modeling approaches.  The emphasis is put on examining if and how vehicle operating characteristics and traffic control strategies have been incorporated into GHG emission modeling and control.  This task first synthesizes the advantages and disadvantages, operational conditions, and scope of each GHG emission data collection methods. Then, the emission modeling approaches that are able to conduct GHG emission analysis and have particular strength in assisting traffic management assessment are investigated, including each model’s capabilities, level of data input, ease of use, and limitations. The traffic simulation models that are able to generate vehicle operating data under different driving conditions are also examined. Finally, research needs for this project are identified based on the review study.

Task 2: Develop Methodologies and Data Collection Plan
This task will first develop a framework and procedure for developing a VSP-based mobile source GHG modeling approach.  Then, it will design a detailed data collection plan that will include:

1. The amount and type of field data that will be needed for model development;
2. Data collection devices, procedures, and protocols; and
3. Testing vehicles, routes, and durations.

The design of the testing route will base on roadway classification, road conditions, and average traffic flow on each roadway.  It is aimed that the designed testing route is able to represent the testing area’s typical traffic conditions, as well as depict traffic management strategies at different levels.

Task 3: Collect Vehicle Activity and Emission Data
This task will implement the data collection plan developed in Task 2.  The most advanced and recent version of PEMS equipment Axion will be used to collect second-by-second real-world vehicle activity and emission data.  The driving patterns, such as the time and the frequency of cold start and engine flameout will be designed based on different traffic management strategies.  At the end of each test, the collected data will be exported to the computer, combined and aligned in spreadsheet files for further analysis.

Task 4: Establish GHG Emission Database
This task will establish a GHG emission database based on the tested data collected in Task 3.  The following data will be included in the database:

1. Vehicle information data, including vehicles’ year, model, license plate number, VMT, emission control standard, engine model, engine displacement, engine revolution, the number of cylinders, and oil supply system, and
2. On-board emission measurement data, including testing date, time, second-by-second vehicle position, vehicle speed, acceleration/deceleration, instantaneous GHG emissions, and fuel consumption.

A data quality control process will be conducted before the establishment of the database. 

Task 5: Develop a VSP-based Mobile Source GHG Modeling Approach
This task will develop a VSP-based mobile source GHG emission modeling approach to analyze GHG emissions under various real-world vehicle operational conditions.  The GHG emissions database established in Task 4 will be further categorized according to roadway classification (major arterials, minor arterials, collectors, and local roads) and roadway types (roadway segment, intersection, on and off ramps, etc.).  Then, VSP will be incorporated in calculating GHG emissions in each particular roadway class and roadway type.  In this process, mathematical and statistical methods will be used to capture GHG emission characteristics under different driving patterns.  The proposed approach will focus on deriving the basic emission factors (BEF) of GHG and analyzing how environmental factors such as season and temperature, vehicle age, VMT, and vehicle emission control standards affect GHG emissions in different VSP intervals.

Task 6: Evaluate the Developed GHG Modeling Approach
This task will evaluate the effectiveness of the GHG modeling approach developed in Task 5.  The evaluation will be carried out in the following steps:

1. Determine the traffic management strategies that will participate in this analysis, such as signal coordination, high occupancy vehicle (HOV) lane configuration, one-way street designation, easy pass application, etc.;
2. Collect real-world GHG emission data before and after the implementation of the selected traffic management strategies; and
3. Compare the results generated from the proposed modeling approach and the GHG modeling approaches identified in Task 1 with real-world data analysis results.

Task 7: Develop GHG Emission Reduction Related Traffic Management Evaluation Methods
This task will develop evaluation methods on traffic management strategies in terms of GHG emission control.  The modeling approach developed in Task 5 will be applied in the emission measurement.  By quantifying and comparing the amount of GHG emissions generated before and after the implementation of each traffic management strategy, the evaluation on the impact of traffic management on GHG emissions can be conducted.

Task 8: Document Research Results and Findings
The purpose of this task is to develop documentation on all research findings from Tasks 1 to 7.  Documentation will include a Research Report containing detailed documentation of the work accomplished, methods used, and results achieved.  It will contain an introduction about the database established, a presentation about the development and evaluation of VSP-based mobile source GHG modeling approach, and detailed description about GHG emission reduction related traffic management evaluation methodologies.

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