A Statistical Characterization of School Bus Drive Cycles Collected via Onboard Logging Systems

In an effort to characterize the dynamics typical of school bus operation, National Renewable Energy Laboratory (NREL) researchers set out to gather in-use duty cycle data from school bus fleets operating across the country. Employing a combination of Isaac Instruments GPS/CAN data loggers in conjunction with existing onboard telemetric systems resulted in the capture of operating information for more than 200 individual vehicles in three geographically unique domestic locations. In total, over 1,500 individual operational route shifts from Washington, New York, and Colorado were collected. Upon completing the collection of in-use field data using either NREL-installed data acquisition devices or existing onboard telemetry systems, large-scale duty-cycle statistical analyses were performed to examine underlying vehicle dynamics trends within the data and to explore vehicle operation variations between fleet locations. Based on the results of these analyses, high, low, and average vehicle dynamics requirements were determined, resulting in the selection of representative standard chassis dynamometer test cycles for each condition. In this paper, the methodology and accompanying results of the large-scale duty-cycle statistical analysis are presented, including graphical and tabular representations of a number of relationships between key duty-cycle metrics observed within the larger data set. In addition to presenting the results of this analysis, conclusions are drawn and presented regarding potential applications of advanced vehicle technology as it relates specifically to school buses. CITATION: Duran, A. and Walkowicz, K., "A Statistical Characterization of School Bus Drive Cycles Collected via Onboard Logging Systems," SAE Int. J. Commer. Veh. 6(2):2013, doi:10.4271/2013-01-2400. In an effort to better understand the operating INTRODUCTION characteristics of school buses across the country and Understanding vehicle usage plays a fundamental role in examine the dynamics challenges associated with the school assessing the performance potential of new vehicle bus vocation, National Renewable Energy Laboratory technologies, leading to more informed decision making, (NREL) researchers, with the cooperation of local school better test procedures [1, 2, 3, 4, 5, 6, 7], more commercially districts and Zonar Systems, collected drive cycle information successful designs, and lowered manufacturing and operating on class 6 and 7 school buses operating in three unique expenses. Of the methods available for modeling vehicle geographic locations. The class 6 and 7 school buses, with usage, operational drive/duty cycles have shown the ability to typical capacities of 71 to 84 passengers, were located in the accurately represent vehicle operating information in an states of Washington, New York, and Colorado. Although efficient and streamlined manner well suited to downstream smaller-sized vehicles exist that fall under the vocational analysis [8, 9, 10, 11, 12, 13, 14, 15, 16, 17]. Typically category of school buses, no data was collected or examined consisting of speed and time information, these seemingly associated with this special subset, as vehicles falling within simple pieces of information, when properly understood, this group display operating characteristics dissimilar to their have been used to assess the value of new technology and to larger counterparts. aid in corresponding development and deployment. NREL/CP-5400-60068. Posted with permission. Presented at the SAE 2013 Commercial Vehicle Engineering Congress. Duran et al / SAE Int. J. Commer. Veh. / Volume 6, Issue 2(October 2013) Upon completion of the data collection phase of this study, detailed drive cycle analysis were performed to characterize typical school bus operating behavior. Examining a number of metrics associated with vehicle energy consumption and driving behavior, statistical relationships between key metrics of interest were explored, and representative standard chassis dynamometer test cycles were chosen corresponding to high, average, and low driving aggressiveness.