SWUTC Research Project Description

Title of Project: PEMS-based Approach to Developing and Evaluating Driving Cycles for Air Quality Assessment

Project Number:  169300

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

Project Monitor:
David Miller
Clean Air Technologies International, Inc.
819 East Ferry St.
Buffalo, NY  14211
(716) 893-5800

Project Status:  Active

Date Started:  9/1/08

Estimation Completion Date:  8/31/09

Estimated Cost - Current Fiscal:  $33,500

Estimated Cost - Total Planned:  $33,500

Project Summary:
Project Abstract:
A driving cycle is the fundamental concept in conducting the emission testing and modeling.  The quality of a driving cycle is directly associated with the accuracy of any air quality analysis, and therefore whether the emission reductions can be achieved.  In the past years, numerous driving cycles have been developed for a variety of practical purposes, while the development of the Environmental Protection Agency (EPA) approved national standard emission factor model MOBILE 6 uses the Federal Test Procedures (FTP) driving cycles, which were legally established in the Federal Codes.  These widely used driving cycles bring considerable uncertainties when the emission estimation is carried out for a specific city or region.  Further, the existing driving cycles have been developed based only on the driving activities, e.g. speed profiles of vehicles, without capturing the characteristics of emission profiles.  In this context, the proposed research is intended to achieve two primary objectives. The first objective is to develop driving cycles for classified roads incorporating a vehicle’s both driving activities and emission characteristics, using the data collected by Portable Emission Measurement System (PEMS), which was not either available or has never been used in developing driving cycles.  Houston is used in the case study for this purpose. A comprehensive database will be established for the collected data and a sophisticated computer program will be developed to generate the specific driving cycles.  The second objective is to develop an evaluation approach of driving cycles in which the Vehicle Specific Power (VSP), a parameter that can readily connect the driving modes with emissions, is used to evaluate how well the driving cycles can represent the driving and emission characteristics on real roads. The proposed methodology for generating driving cycles will then be evaluated for its effectiveness on the emission estimation based on a comparative analysis with the current emission inventory and the other methodologies.   The conclusions from this research will help establish a more accurate approach for developing emission inventories and therefore are of significant to the effort of emission reductions.

Project Objectives:

• employ PEMS to collect abundant on-road emission and driving data to make a comprehensive emission and driving database,
• develop driving cycles for classified roads considering both driving conditions and emission characteristics,
• develop a VSP-based evaluation method for driving cycles, which is applied to the driving cycles developed in this research, and
• compare driving cycles developed in this research with driving cycles developed by traditional method to demonstrate the significance to incorporate emission characteristics in developing driving cycle

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 the development and evaluation of driving cycles.  Special attention will be paid on whether the development of any existing driving cycles has considered the elements of vehicle emissions.  This task will synthesize strengths and weaknesses of current methodologies and practices, and then identify the research needs for this project. The areas to be reviewed include:

• Methodologies for developing driving cycles based on a variety of criteria,
• Field data collection and analysis for driving cycles, and
• Evaluation measures of driving cycles.

Task 2: Develop Methodologies and Data Collection Plan
This task will first develop a framework and procedures for developing driving cycles by incorporating parameters that are directly related to vehicle emissions.  Then, it will develop a detailed data collection plan that will include:

• the need of field data for developing driving cycles,
• the data collection devices, procedures and protocols, and
• the testing vehicles, routes, and durations.

Task 3: Collect Vehicle Activity and Emission Data
This task will implement the data collection plan developed in Task 2.  The car chasing method will be used. The driver of the instrumented car will be informed to follow the motion of a specific type of vehicle during each test run to simulate the driving patterns of the target vehicle.

The most advanced and recent version of the Portable Emission Measurement System (PEMS), Montana OEM-2100 is used to collect real-world vehicle activities and emissions data.  The Global Positioning System (GPS) receiver, GeoLogger, will be used to collect the route position and velocity information, as well as the precise time on a second-by-second basis.  

At the end of each testing, the collected vehicle activity and emission data by OEM-2100 and GeoLogger will be downloaded to the computer, combined and aligned in spreadsheet file, and finally imported to ACCESS database for further analysis.

Task 4: Develop Driving Cycles based on the Tested Data
This task will develop driving cycles based on tested data collected in Task 3 and the methodologies developed in Task 2. Driving cycles will be developed according to the variables of driving modes including proportion of idling, acceleration, deceleration, mean speed, maximum speed, etc., as well as emission related parameters, which are new in this research.

The task will be conducted following these steps:

• Classify test data into groups based on testing facility types;
• Split each group into microtrips;
• Calculate pre-defined parameters, such as proportion of idling, mean speed, etc., for each microtrip;
• Calculate emission factors for each microtrip,
• Synthesize above characteristic parameters as criteria to select the most representative microtrips; and
• Generate driving cycles by splicing the candidate microtrips.

Microtrips are defined as segments of consecutive speed data that begin and end with at least two consecutive seconds of zero speed. The end of a microtrip is marked by one second of zero speed. Any additional seconds of zero speed are included as the beginning of the next microtrip.

Task 5: Evaluate Driving Cycles for the Purpose of Emission Estimation
This task will evaluate the driving cycles developed in Step 4.  The existing methods identified in the literatures for developing driving cycles will also be used to develop driving cycles using the data collected in Houston.  The emission factors of Houston will be estimated according to driving cycles developed by both the proposed and the existing methodologies.  Finally, the driving cycles will be compared and evaluated for the purpose of emission estimation.  Vehicle specific power (VSP) distributions and statistical analysis will be used in this task.

Task 6: Prepare Final Report, Deliver and Present Models
The purpose of this task is to develop documentation on all research findings from Tasks 1 to Task 5.  Documentation will include a Research report containing detailed documentation of the work performed, methods used, and results achieved.  It will contain the developed driving cycles for Houston, the evaluation methodologies, and the sensitive analysis on emission estimations.

Index Terms:
Air quality management, Pollutants, Portable Emissions Monitoring System, Exhaust gases, MOBILE6 (Computer model), Data collection, Research projects