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The performance of several aerodynamic technologies and approaches, such as trailer skirts, trailer boat tails, gap reduction, was evaluated using track testing, model wind tunnel testing, and CFD simulation, in order to assess the influence of the design, position and combination of various aerodynamic devices. The track test procedure followed the SAE J1321 SAE Fuel Consumption Test Procedure - Type II. Scale model wind tunnel tests were conducted to have direct performance comparisons among several possible configurations. The wind tunnel tests were conducted on a 1/8 scale model of a tractor in combination with a 53-foot semi-trailer. Among others, the wind tunnel tests and CFD simulations confirmed the influences of trailer skirts' length observed during the track tests and that the wider skirt closer to the ground offer better results. The differences in the shape, dimensions and position of rear deflectors and trailer skirts on the trailer are reflected in the test results.

The conditions of vehicle use are among the most important factors affecting the fuel consumption. Such conditions may include payload, type of duty cycle, traffic density, number of stops and starts, type of pavement, and use of auxiliary systems. Transport companies are interested in results from experiments reproducing similar operational conditions to help them understand and quantify the impact of duty cycles on fuel economy and operating costs. The goal of this study was to evaluate the effect of driving cycle on fuel efficiency. The fuel consumption measurement methodology was based on the protocols described in SAE J1321 Fuel Consumption Test Procedure - Type II and SAE J1526 Fuel Consumption Test Procedure (Engineering Method). The tests were conducted with various vehicles under different test conditions. Several duty cycles were replicated on the track, such as a local delivery, regional transport, long-distance constant speed, and stop-and-go cycles.

Commercial fleets are interested in results from experiments conducted in real operational conditions to help them quantify and understand the impact of environmental factors on fuel economy and operating costs. The goal of this study was to measure through controlled track testing and operational testing the effects of environmental conditions, particularly ambient temperature, and air density, on fuel consumption. Extensive track testing based on the SAE J1321 Fuel Consumption Test Procedure - Type II protocol with various vehicles under different test conditions showed a decrease in fuel efficiency of up to 12% for an air density variation of 7% and an ambient temperature variation of 30 °F (17 °C). Data from various and extensive operational tests were also analyzed, specifically from tests conducted using several groups of medium and heavy-duty vehicles involved in regional, local, urban transport and pick-up and delivery.

This study aimed to evaluate several rolling resistance reduction measures applicable to class 8 tractor-trailer combinations. Two methods have been employed: fuel consumption tests according to the SAE J1321 Joint TMC/SAE Fuel Consumption Test Procedure - Type II, and long-term operational observations using control and test vehicles monitored throughout baseline and test periods. One way to reduce the rolling resistance is to use wide-base tires: two different Type II fuel consumption tests revealed a more than 9 % improvement in fuel economy for a tractor-trailer combination equipped with wide-base tires. Long-term operational observation assessed the use of single wide-base tires on two 8-axle B-train tractor-trailer combinations. The results showed an average 5.11% fuel improvement and an average 4.37% energy intensity improvement. Other tests compared single-wide base tires with different tread patterns and tire compounds.

The objective of this project was to compare the fuel consumption and traction performances of 6 × 2 and 6 × 4 Class 8 tractors. Two approaches have been considered: evaluation of 6 × 2 tractors, modified from 6 × 4 tractors, and evaluation of OEM 6 × 2 tractors. Compared to the 6 × 4 tractors, which are equipped with a rear tandem with both drive axles, the 6 × 2 tractors have a rear tandem axle with one drive axle, and one non-drive axle, also called dead axle. The 6 × 2 tractor configurations are available from the majority of Class 8 tractor manufacturers. The SAE Fuel Consumption Test Procedures Type II (J1321) and Type III (J1526) were used for fuel consumption track test evaluations. Traction performances were assessed using pull sled tests to compare pulling distance, maximum speed, and acceleration when pulling the same set sled on similar surface.