Opinion ID: 480337
Heading Depth: 2
Heading Rank: 1

Heading: Road Load Power Settings

Text: 21 Fuel economy is tested in the laboratory under simulated road conditions. The laboratory conditions cannot totally duplicate the open road, but they do produce consistent and replicable results that approximate on-the-road driving. The first retroactive CAFE dispute arises out of attempts to make these laboratory conditions more realistic. 22 Road load power is the amount of power that is required to overcome resistance and keep an automobile traveling steadily at fifty miles per hour. During laboratory testing, which is conducted on a set of dynamometer rollers on which the vehicle's wheels must turn, a power absorption unit is adjusted to reflect the amount of road load power that a particular vehicle requires to overcome resistance. The setting will necessarily vary from model to model. For MY 1975, two methods of setting vehicle road load were available to manufacturers, although one--a table of settings relating vehicle weight to road load power 12 --was predominantly used. The alternative method, which measured manifold intake pressure, 13 was used that year only by manufacturers whose vehicles incorporated a more advanced aerodynamic design. That method became impractical soon thereafter because changes in emission control techniques interfered with its use. 23 In 1976, the EPA announced that the coastdown method, among others, would be considered an acceptable alternative method of measuring road load. 14 The coastdown method, like the manifold intake method, credited a vehicle's aerodynamic efficiency. It is undisputed in this litigation that the two methods yield comparable results. Nonetheless, petitioners label the coastdown announcement a test procedure change, arguing that the manifold intake procedure was not a part of the MY 1975 yardstick, since virtually no manufacturer used it that year. We disagree with petitioners' conclusion. 24 The critical fact is that a procedure that credited reductions in a vehicle's road load power requirements achieved through improved aerodynamic design was available for MY 1975 testing, and those manufacturers, however few in number, that found it advantageous to do so, employed that procedure. The manifold intake procedure subsequently became obsolete for other reasons, but its basic function, to measure real improvements in fuel economy through more aerodynamically efficient designs, lived on in the form of the coastdown technique for measuring these aerodynamic improvements. We credit the EPA's finding that increases in measured fuel economy because of the lower road load settings obtainable under the coastdown method, were increases likely to be observed on the road, and were not unrepresentative artifact[s] of the dynamometer test procedure. 15 Such real improvements are exactly what Congress meant to measure when it afforded the EPA flexibility to change testing and calculating procedures. 16 We agree with the EPA that no retroactive adjustment need be made on account of the coastdown technique.