Freight transportation is essential to maintaining commerce and economies in the United States and globally. However, freight transportation is known to have significant environmental and public health impacts. Harmful emissions of carbon dioxide, methane, hydrofluorocarbons, and black carbon increase the risk of global climate change. Emissions of nitrogen oxides and particulate matter contribute to serious public health risks including increased incidences of premature death, and increased severity of respiratory and cardiovascular illness. As trade is increasingly globalized and economies expand, harmful air emissions from goods movement are projected to increase at faster rates than all other sources of transport-related emissions. While mandatory rules such as advanced vehicle emission and fuel quality standards reduce emissions from new vehicles, the vast legacy fleet of heavy duty diesel vehicles present a challenge for policy makers around the world. This paper examines how a voluntary policy model, the U.S. Environmental Protection Agency’s SmartWay Transport Partnership, fosters behavior change, facilitates strategic interactions and enables more informed decision-making in the freight sector to improve performance and reduce emissions. The effectiveness of this innovative model has generated international interest and led to program replication in other countries.

We hypothesize that components designed to improve fuel economy by reducing power requirements should also result in a decrease in emissions of oxides of nitrogen (NOx). Fuel economy and NOx emissions of a pair of class 8 tractor-trailers were measured on a test track to evaluate the effects of single wide tires and trailer aerodynamic devices. Fuel economy was measured using a modified version of SAE test procedure J1321. NOx emissions were measured using a portable emissions monitoring system (PEMS). Fuel consumption was estimated by a carbon balance on PEMS output and correlated to fuel meter measurements. Tests were conducted using drive cycles simulating highway operations at 55 mph and 65 mph and suburban stop-and-go traffic. The tests showed a negative correlation (significant at p < 0.05) between fuel economy and NOx emissions. Single wide tires and trailer aerodynamic devices resulted in increased fuel economy and decreased NOx emissions relative to the baseline tests. Decreases in NOx emissions were disproportionately larger than increases in fuel economy; however, this effect may be an artifact of the particular engine being tested. These results demonstrate that emissions reductions can be achieved using strategies that decrease fuel use and save truck operators money.

Current SAE practices for evaluating potential improvements in fuel economy on heavy-duty vehicles rely on gravimetric measurements of fuel tanks. However, the recent evolution of portable emissions measurement systems (PEMS) offers an alternative means of evaluating real-world fuel economy that may be faster and more cost effective. This paper provides a direct comparison of these two methods based on a recent EPA study conducted at Southwest Research Institute. More than 228 on-road tests were performed on two pairs of class 8 tractor-trailers according to SAE test procedure J1321 in an assessment of various chassis components designed to reduce drag losses on the vehicle. During these tests, SEMTECH-D™ portable emissions measurement systems from Sensor's, Incorporated were operating in each of the vehicles to evaluate emissions and to provide a redundant measure of fuel economy. These measurements showed excellent correlation to the gravimetric results with a coefficient of determination greater than 0.98 and nearly identical regression slopes for three of the four trucks. One truck had a series of suspect data toward the end of the study that biased the regression slope higher by 4%. Measurement variability also compared favorably between the two test methods. The average coefficient of variation based on the three repeat laps performed on every test segment was 2.98% for the gravimetric measurements and 3.26% for the SEMTECH-D measurements at a 95% confidence interval. These results all support the use of SEMTECH-D as a viable alternative to the gravimetric measurements for heavyduty in-use fuel economy determination.

Reducing aerodynamic drag and tire rolling resistance in trucks using cooled EGR engines meeting EPA 2004 emissions standards has been observed to result in increases in fuel economy and decreases in NOx emissions. We report here on tests conducted using vehicles equipped a non-EGR engine meeting EPA 2004 emission standards and an electronicallycontrolled engine meeting EPA 1998 emissions standards. The effects of trailer fairings and single-wide tires on fuel economy and NOx emissions were tested using SAE test procedure J1321. NOx emissions were measured using a portable emissions monitoring system (PEMS). Fuel consumption was estimated by a carbon balance on PEMS output and by the gravimetric method specified by test procedure J1321. Fuel consumption decreased and fuel economy increased by a maximum of about 10 percent, and NOx emissions decreased by a maximum of 20 percent relative to baseline. This compares with NOx reductions of up to 45 percent reported in the earlier test on the cooled EGR engine. The reduction in power requirements in the current test did not result in a corresponding reduction in brake specific NOx emissions, as it did in the earlier test. These results provide further evidence that reducing parasitic losses in heavy-duty highway vehicles will not only reduce fuel consumption and greenhouse gas emissions, but will also provide NOx reductions that pay for themselves through reduced fuel use.