Summary	of	Interagency	Working	Comments	on	Draft	Language	under	EO	

12866	and	EO	13563	Interagency	Review.		Subject	to	Further	Policy	Review.

Interagency	Comments	on	U.S.	Environmental	Protection	Agency	(EPA)	and	National	

Highway	Traffic	Safety	Administration	(NHTSA)	draft	proposed	rule	titled,	“Greenhouse	Gas	

Emissions	and	Fuel	Efficiency	Standards	for	Medium- and	Heavy-Duty	Engines	and	Vehicles	-

Phase	2.”		RIN	2060-AS16;	RIN	2127-AL52

General

 Is EPA assuming 100% deployment of the technologies from the Heavy Duty Phase 1 rule? Suggest that 

the agency take comment on the level of Phase 1 penetration as it does not appear that this has yet to be 

achieved in the market.

 Suggest that EPA take comment on how representative the powertrain calibrations are that are used in 

GEM that would allow manufacturers the use this data instead of steady state fuel maps. 

 Pg 99 has some language on idle reduction. The commenter requests that the agencies include 

exemptions for manlifts and cranes. If an automatic engine shutdown is installed, idle reduction rules 

could potentially lead to safety issues for larger boom equipment as they require the engine to drive the 

hydraulic system and thus be able to move and raise/lower the manlift and crane.

 Pg 51 discusses low rolling resistance tires. The commenter requests an exemption for vehicles that 

operate primarily off road (such as equipment on Rights of Way (ROW)). The commenting agency has 

had issues in the past with EPA noise limitations due to some of the additions that were installed on 

equipment to allow them to operate off road.

 For federal agency off road vehicle fleets, the ambiguity in the documents due to lack of specifics, 

especially for technology that isn’t commercially available yet, is concerning as the commenter does not 

know where any of this equipment would be placed on the vehicles. The commenting agency has vehicle 

travel height issues even today, and if aerodynamic or other components are added in response to this 

rule that reduce road clearance under the vehicle, it will have an negative impact due to potential damage 

to these systems and subsequent breakdown of off road use vehicles. 

 The commenter is concerned that more systems on these trucks means more training for our technicians 

and more maintenance for the systems in already tight budgets. As we serve the public, this will result in 

higher operational costs for our rate payers.

 Expansion of alternative fuel requirements with no commercial infrastructure could result in the agency

having to put in place more alternative fuel infrastructure adding to our costs (i.e. our customers' cost) 

for both the facilities as well as their maintenance, not to mention the potential environmental impacts. 

Payback Periods

The commenter requests the agencies to consider these technologies that would likely offer deeper savings 

although with higher paybacks. 

 VTO tractor-trailer economic models assume a payback curve with a 1-2 year preferred payback 

(~84% of owners at 2 years or less). At 3 years, the adoption rate falls to 22%. However, the 

commenter’s models do not assume the forcing function of the regulation, instead relying solely on 

market forces.

 For trailers, the ownership period is likely much longer. However, the trailers often are not owned 

by the same company that purchases/leases the tractor and pays the fuel bill. And again, the agency 

analysis has focused solely on market forces without the overlay of regulation.

 For vocational vehicles, a six-year payback may make economic sense because of the longer 

ownership periods. However, this is a longer period than typical financial planning horizons, 

particularly for businesses that operate with slim margins.
Certification and Compliance Comments

 Data. Regulations and impact assessments are best supported by sound data and analysis. The age

of the Vehicle Inventory and Use Survey (VIUS) data is well known, and there is the general belief 

that the market has changed considerably since the last survey (13 years ago). There are additional 

issues with VIUS relating to sampling, selection, and the reliability of self-reported data. It is not 

completely transparent how the forecasts were set beyond use of the MOVES model and DOT 

CAFE model. It was not clear how second purchasers of vehicles were considered. Additionally, it is 

not clear what plans there are for in-use confirmation of regulatory impacts, if any. Assuming VIUS 

survey updates are not available going forward, the commenter recommends that the agencies clarify 

the methodology used for sampling, forecasts, and whether pursuing some type of in-use data 

collection or survey would have any practical utility.

 GEM. The improved features and flexibility of the GEM model are evident, yet the commenter

notes that the usefulness of the tool is limited to technologists and suggests the agencies make it 

more layman friendly. The commenter notes that for customer guidance, the OEM simulation tools 

for specifying trucks for first-purchasers will remain more accessible, detailed and accurate for realworld analysis than GEM. For buyers of used trucks, an online, user-friendly truck simulation is not 

currently available.

 Transparency/on-line tool (based on GEM). We agree that analysis tools for trucking companies 

are very useful. However, it is not likely that GEM could form the basis of these tools. As a 

simulation model, it seems as the new version of GEM will require a lot of testing / analysis for the 

OEMs to get the required inputs. Users who are closer to the market would want something much 

simpler based on actual product offerings (like FuelEconomy.gov) but with pre-loaded usage 

profiles. A significant step for truck operators achieving optimized fuel efficiency is getting the 

vehicle specified right for the intended job (engine, transmission, axle, etc). This step normally 

happens at the vehicle dealer. 

Engine Targets and Test Procedures

 Conversion factors. It would be preferred to include conversions between various parameters such 

as g/hp-h CO2 to efficiency or Brake Specific Fuel Consumption (BSFC). 

 Undervalued Combustion. Combustion optimization is reported as one of the smaller 

contributors to improved fuel consumption, even at the end of the rule period (2027). Overall, the 

language seems to short-sell how essential combustion optimization is as an efficiency multiplier and 

in achieving criteria emissions requirements. Also this section does not adequately emphasize 

increasing cylinder pressures and Brake Mean Effective Pressure (BMEP) to achieve higher engine 

efficiency. There is no mention of materials improvements or thermal management that is likely 

required to achieve higher engine efficiency. There is a notable absence of discussion of novel 

engine configurations or kinetic-dominated combustion modes (HCCI, RCCI, etc). 

 Undervalued Turbochargers. The section understates importance of devices with higher 

efficiency and higher boost capability. The SwRI modelling showed that a 5% improvement in 

turbocharger efficiency would yield about 2% fuel consumption reduction. It is not clear why this 

was not addressed, noting that this is not the same or redundant with turbocompounding.

“Alternative” Fuel Considerations

 Natural gas engines. Natural gas engines will have the same engine GHG standard as diesel 

engines with which they compete. Since the OEMs can now add their own engine map to GEM, we 

presume (but is not clear) that this includes natural gas engines so the certification can be the same as 

for diesel and gasoline powered trucks, and noting that there was no natural gas engine map in Phase 

1 GEM. However, we did not see this spelled out in the Notice of Proposed Rulemaking (NOPR).
 Gasoline-fueled HD option. Since these regulations cover vehicles out to at least 2027, the 

commenter recommends that the Agencies consider the emergence of high-efficiency gasolinefueled, but diesel-platform engines that would be economically attractive to operators. These would 

essentially be gasoline versions of today’s natural gas HD engines with low-cost Three-Way Catalyst 

(TWC) aftertreatment and low-cost fuel. Fuels with higher octane are also a potential enabler of this 

approach. Gasoline compression-ignition is a longer term alternative gasoline-fueled option.