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NHTSA and EPA Responses to Interagency Line Item 

Comments on Rebound Section of HDV Phase 2 NPRM 

Preamble Received on May 29, 2015

OMB suggested edits = red 

Draft Agencies’ edits = blue 

Edit #1

“For example, the owners and operators of LDVs would likely view may respond 

to the costs and benefits associated with changes in their personal vehicle’s fuel 

efficiency very differently than a HDV fleet owner or operator would view the 

costs and benefits (e.g., profits, offering more competitive prices for services) 

associated with changes in their HDVs’ fuel efficiency. “To the extent the 

response differs, such differences may be smaller for The potential exception is

HD pick-ups and vans, which share some similarities with LDV.”

Draft Agencies’ Response: We accept these edits.

Comment A1/Edit #2

“Alternatively, HDV operators could simply use fuel savings to spend more on 

other costs such as driver labor or vehicle capital (e.g., holding freight output 

constant), which may not result in higher VMT.” 

A1: Commenters understand that this behavior, as described here, would not be consistent with 

profit maximization in a competitive market. No profit maximizer takes savings from one input 

and gives it to another input for no apparent reason. Commenter requests that you either please 

either delete or provide a testable explanation of how it is in fact consistent with profit 

maximization.

Draft Agencies’ Response: We accept this deletion. 

Edit #3

“For example, customers might demand more ship more frequently shipments, 

ship products or materials over longer distances, or shift traffic to HDVs from 

other shipping modes such as rail, barge or air.”

Draft Agencies’ Response: We propose the following revision to replace that suggested by

Interagency Commenters: 

“For example, customers might order more frequent shipments or choose products that 

entail longer shipping distances, while freight carriers might divert some shipments to 

trucks from other shipping modes such as rail, barge or air.”
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Comment A2/Edit #4

“Conversely, if fuel efficiency standards lead to net increases in the total costs of 

HDV operation because fuel cost savings do not fully offset the increase in HDV 

purchase prices and associated depreciation costs, then the price of HDV services 

could rise. This is likely to spur a decrease in HDV VMT, and perhaps a shift to 

alternative shipping modes. These effects could also ripple through the economy

and affect GDP.”

A2: Commenters note that for this to be the case wouldn’t technology costs have to be greater 

than after-tax fuel process? Is that consistent with the analysis supporting the rule?

Draft Agencies’ Response: We are not suggesting that technology costs fully offset fuel cost 

savings, only discussing the fact that technology costs are an important factor that can affect the 

magnitude of the rebound effect. We reject the deletion of this sentence, however, we will 

clarify that we assume fuel savings fully offset technology costs in our analysis supporting the 

NPRM:

“Conversely, if fuel efficiency standards lead to net increases in the total costs of 

HDV operation because fuel cost savings do not fully offset the increase in HDV 

purchase prices and associated depreciation costs, then the price of HDV services 

could rise. This is likely to spur a decrease in HDV VMT, and perhaps a shift to 

alternative shipping modes. These effects could also ripple through the economy

and affect GDP. Note, however, that we project fuel cost savings will offset 

technology costs in our analysis supporting our proposed standards.”

Comment A3

Commenters note that all of the points made in this paragraph taken together appear to indicate 

UNCERTAINTY, but not necessarily unequivocal BIAS in a particular direction as it might be 

applied to the U.S. Commenters note that it is not sufficient to establish a degree of uncertainty 

with regard to their application to the U.S. the agencies must establish unambiguous and 

substantial bias in these estimates for purposes of applying to this rule. Commenters do not see 

sufficient justification for giving it zero weight in the analysis of this rule.

Draft Agencies’ Response: We agree with the commenter that there is not necessarily an 

unequivocal bias in the two studies (Matos and Silva; De Borger and Mulalic). Our discussion 

of these two studies was intended to emphasize the uncertainly regarding their application to our 

proposed standards, rather than uncertainty surrounding their empirical results. We note, 

however, that we did not give these studies "zero weight" as the commenter suggests; we took 

these studies and all the studies we discuss in the preamble into consideration when selecting our 

proposed Phase 2 values. As we discuss in the preamble, we did not find these two studies - or 

any other study we became aware of since the Phase 1 rule – sufficiently compelling to propose 

using different values from those that we used in Phase 1. 
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Comment A4

Previous comment applies here as well.

Draft Agencies’ Response: See response to Comment A3.

Comment A5

Commenters request clarity on relevance of this point. Once again this indicates uncertainty but 

there is no substantiated claim they are biased in one direction of another.

“Volpe analysts tested a large number of different specifications for its national 

and state level models that incorporated the effects of factors such as aggregate 

economic activity and its composition, the volume of U.S. exports and imports, 

and factors affecting the cost of producing trucking services (e.g., driver wage 

rates, truck purchase prices, and fuel costs), and the extent and capacity of the 

U.S. and states’ highway networks. Table XX summarizes Volpe’s Phase 1 

estimates of the elasticity of truck VMT with respect to fuel cost per mile.19 As it 

indicates, these estimates vary widely, and the estimates based on state-level and 

national data differ substantially.”

Draft Agencies’ Response: The paragraph is intended to provide a description of the analysis 

performed and the results. It is not intended conflate bias and uncertainty. We are simply 

discussing the fact that the estimates vary widely; we are not suggesting a bias in one direction or 

another. 

Comment A6

Presumably it will be available for the final rule, no? Commenters request clarity on Why not lay 

out here and seek comment?

“Volpe staff conducted additional analysis of the models that yielded the 

estimates of the elasticity of truck VMT with respect to fuel cost per mile reported 

in Table XX, using updated information on fuel costs and other variables 

appearing in these models, together with revised historical data on truck VMT 

provided by DOT’s Federal Highway Administration. The newly-available data, 

statistical procedures employed in conducting this additional analysis, and its 

results are summarized in materials that can be found in the docket for this 

rulemaking. This new Volpe analysis was not available at the time the agencies 

selected the values of the rebound effect for this proposal, but the agencies will 

consider this work and any other new work that becomes available in the final 

rule.”

Draft Agencies’ Response: This analysis is on-going and is expected to be docketed before the NPRM 

is published.
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Comment A7

Is this evidence on the responsiveness of truck use, vehicle use, or aggregate energy use? 

Commenters suggest clarifying whether this literature is directly applicable to heavy trucks.

“Similarly, there is some evidence in the literature that demand for fuel is more 

responsive to fuel price increases than to decreases.22”

22Gately, D. 1993. The Imperfect Price-Reversibility of World Oil Demand. The Energy Journal, 

International Association for Energy Economics, vol. 14 (4), pp. 163-182; Dargay, J.M., Gately, 

D. 1997. The demand for transportation fuels: imperfect price-reversibility? Transportation 

Research Part B 31(1); and Sentenac-Chemin, E., 2012. Is the price effect on fuel consumption 

symmetric? Some evidence from an empirical study. Energy Policy, vol. 41, pp. 59-65. 

Draft Agencies’ Response: The three studies cited respectively address the responsiveness of 

world oil consumption, gasoline, diesel, and LPG consumption, and gasoline consumption to 

changes in prices for petroleum, gasoline, and gasoline. We can clarify the sentence as follows: 

“Similarly, there is some evidence in the literature that demand for crude 

petroleum and refined fuels is more responsive to increases than to decreases in 

their prices, although this research is not specific to the HDV sector.

Edit #5

“This is because the United States has extensive rail, waterway, pipeline, and air 

transport networks in addition to an extensive highway network; these networks 

often closely parallel each other and are often viable choices for freight transport 

for many long-distance shipping routes within the continental U.S. If rates for one 

mode decline, demand for that mode is likely to increase, and some of this new 

demand could represent shifts from other modes.27”

Draft Agencies’ Response: We accept this edit.

Comment A8

Commenters want to know if you mean “differentiate” here?

Draft Agencies’ Response: We will replace “discern” with “differentiate.

“In our assessment, we do not discern differentiate between short-run and longrun rebound effects, although these effects may differ.”