Evaluation of Drayage Truck Chassis Dynamometer Test Cycles and Emissions Measurement

Abstract

In 2006, the ports of Long Beach and Los Angeles adopted the final San Pedro Bay Ports Clean Air Action Plan (CAAP), initiating a broad range of programs intended to improve the air quality of the port and rail yard communities in the South Coast Air Basin. As a result, the Technology Advancement Program (TAP) was formed to identify, evaluate, verify and accelerate the commercial availability of new emissions reduction technologies for emissions sources associated with port operations, [1]. Container drayage truck fleets, an essential part of the port operations, were identified as the second largest source of NOx and the fourth largest source of diesel PM emissions in the ports’ respective 2010 emissions inventories [2, 3]. In response, TAP began to characterize drayage truck operations in order to provide drayage truck equipment manufacturers with a more complete understanding of typical drayage duty cycles, which is necessary to develop emissions reduction technologies targeted at the drayage market. As part of the broader TAP program, the Ports jointly commissioned TIAX LLC to develop a series of drayage truck chassis dynamometer test-cycles. These cycles were based on the cargo transport distance, using vehicle operational data collected on a second-by-second basis from numerous Class 8 truck trips over a period of two weeks, while performing various modes of typical drayage-related activities. Distinct modes of operation were identified; these modes include creep, low-speed transient, high-speed transient and high-speed cruise. After the modes were identified, they were assembled in order to represent typical drayage operation, namely, near-dock operation, local operation and regional operation, based on cargo transport distances [4]. The drayage duty-cycles, thus developed, were evaluated on a chassis dynamometer at West Virginia University (WVU) using a class 8 tractor powered by a Mack MP8-445C, 13 liter 445 hp, and Model Year (MY) 2011 engine. The test vehicle is equipped with a state-of-the-art emissions control system meeting 2010 emissions regulations for on-road applications. Although drayage trucks in the San Pedro Bay Ports do not have to comply with the 2010 heavy-duty emissions standards until 2023, more than 1,000 trucks already meet that standard and are equipped with diesel particulate filter (DPF) and selective catalytic reduction (SCR) technology as used in the test vehicle. An overview of the cycle evaluation work, along with comparative results of emissions between integrated drayage operations, wherein drayage cycles are run as a series of shorter tests called drayage activities, and single continuous drayage operation cycles will be presented herein. Results show that emissions from integrated drayage operations are significantly higher than those measured over single continuous drayage operation, approximately 14% to 28% for distance-specific NOx emissions. Furthermore, a similar trend was also observed in PM emissions, but was difficult to draw a definite conclusion since PM emissions were highly variable and near detection limits in the presence of DPF. Therefore, unrepresentative grouping of cycle activity could lead to over-estimation of emissions inventory for a fleet of drayage vehicles powered by 2010 compliant on-road engines.