Evaluation of Road Grade 

Profiles for Cruise Cycles with 

ISX/TC10 Powertrain

James Sanchez

8/31/2015

EPA Draft Analysis
Overview

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-1

1

3

0 5000 10000 15000 20000

Road Grade, %

Test Cycle Distance, m

• In the HD Phase 2 Proposal EPA and NHTSA proposed that the two cruise cycles would also include grade.

• While the agencies worked on a nationally representative road grade profile, the agencies used the road 

grade profile for an actual road in Texas for all the analysis that informed the proposal.

• Now that the work has been completed to create nationally representative road grade profiles, the agencies 

are evaluating the profiles and are seeking feed back from industry on them. 

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40

Elevation, m

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Test Cycle Distance, m

EPA Draft Analysis
Development of Nationally Representative, 

Activity Weighted Road Grade Profiles

• Nationally representative, activity weighted road grade profiles for US restricted access highways were developed by the EPA s 

using the following datasets:

• Half hill* and road grade data generated by NREL using a TomTom database (* Continuous stretch of roadway where grade does not change 

sign)

• Truck activity (VMT) data based on annual reports by individual states and obtained from the 2011 EPA National Emissions Inventory

• The following profiles were created to account for truck speed limit effects:

• 12 mile (19.3 km) profile representing truck speed limit range of 55-75 mph and driven in both directions

• 12 mile (19.3 km) profile representing truck speed limit range of 55-60 mph and driven in both directions

• 12 mile (19.3 km) profile representing truck speed limit range of 65-75 mph and driven in both directions

• 2x6 mile (19.3 km) profile representing truck speed limit range of 55-75 mph

• Each road grade profile consists of half hills representing unique segments of the national half hill population and vehicle activity associated with those segments. The length of each half hill is directly proportional to the VMT it represents. The distribution of 

road grade within each half hill of a profile is a symmetric representation of the actual, activity weighted distribution of road grade within the corresponding segment of the national half hill population

• 2% of the steepest road grades in each half hill road grade distribution were trimmed to the next highest level in order to avoid the extremes

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4

9

7,348 9,348 11,348

Road Grade, %

Test Cycle Distance, m

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0

50

7,348 9,348 11,348

Elevation, m

Test Cycle Distance, m

EPA Draft Analysis
New Road Grade Profiles - %Grade

EPA Draft Analysis
New Road Grade Profiles - Elevation

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0 5,000 10,000 15,000 20,000

Elevation, m

Test Cycle Distance, m

Profile A (Speed limits 55-75 mph)

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20

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0 5,000 10,000 15,000 20,000

Elevation, m

Test Cycle Distance, m

Profile B (Speed limits 55-60 mph)

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-10

0

10

20

30

Elevation, m

0 5,000 10,000 15,000 20,000

Test Cycle Distance, m

Profile D (Speed limits 55-75 mph)

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0 5,000 10,000 15,000 20,000

Elevation, m

Test Cycle Distance, m

Profile C (Speed limits 65-75 mph)

EPA Draft Analysis
Powertrain Test Configurations

• 2012 Cummins ISX 450 HP

• Allison TC10, economy mode

• Simulate vehicles

• Static Mass: 31,978 kg

• Rotating Mass: 1,134 kg

• CdA: 5.4

• Crr: 6.9 g/kg

• Tire Radius: 0.5 m

• Axle Eff.: 95.5%

• Axle Ratios: 2.4, 2.64, and 3.36

Picture of test setup with Eaton AMT

EPA Draft Analysis
55 mph Cycles

360

380

400

420

440

460

480

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

Fuel Consumed (g/mile)

Proposed A - Fwd A - Rvrs B - Fwd B - Rvrs D

195.000

200.000

205.000

210.000

215.000

220.000

225.000

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

bsfc (g/kw-hr)

Proposed A - Fwd A - Rvrs B - Fwd B - Rvrs D

• These results plus those on the next slide show that any of these road grades would have noticeable impacts on the 

numerical values of the standards if one of them is chosen for the final rule, but relative values in % may not be so 

sensitive. Also, since the baseline (reference case) would also use the new profile, the impact on stringency would be 

minimized.

EPA Draft Analysis
65 mph Cycles

195.000

200.000

205.000

210.000

215.000

220.000

225.000

230.000

235.000

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

bsfc (g/kW-hr)

Proposed A - Fwd A - Rvrs C - Fwd C - Rvrs D

420

440

460

480

500

520

540

560

580

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

Fuel Consumed (g/mile)

Proposed A - Fwd A - Rvrs C - Fwd C - Rvrs D

EPA Draft Analysis
Axle Ratio 2.4, Proposed Profile – 55mph

EPA Draft Analysis
Axle Ratio 2.64, Proposed Profile – 55mph

EPA Draft Analysis
Axle Ratio 3.36, Proposed Profile – 55mph

EPA Draft Analysis
Axle Ratio 2.4, Profile B Forward – 55mph

EPA Draft Analysis
Axle Ratio 2.64, Profile B Forward – 55mph

EPA Draft Analysis
Axle Ratio 3.36, Profile B Forward – 55mph

EPA Draft Analysis
Axle Ratio 2.4, Proposed Profile – 65mph

EPA Draft Analysis
Axle Ratio 2.64, Proposed Profile – 65mph

EPA Draft Analysis
Axle Ratio 3.36, Proposed Profile – 65mph

EPA Draft Analysis
Axle Ratio 2.4, Profile C Forward – 65mph

EPA Draft Analysis
Axle Ratio 2.64, Profile C Forward – 65mph

EPA Draft Analysis
Axle Ratio 3.36, Profile C Forward – 65mph

EPA Draft Analysis
Questions for Industry

• Are these grade profiles representative of the cycles used by your company to design/evaluate heavy-duty vehicles?

• Does industry have concern with evaluating all vehicles on a nationally representative 

cycle?

• Are vehicle designs tailored to the regional road grades that the vehicle will be used in or 

are they designed to work across the country?

• Does industry believe that there could be unintended consequences for evaluating 

vehicles on grades above 3% even though they are nationally representative?

• The results presented here show that vehicle speed can drop as low as 45mph. Would 

you expect that many vehicles would drop below 45mph on these road grade profiles?

• Do you prefer 55 and 65mph cycles with different road grade profiles, such as Profile B for 55 mph and Profile C for 65mph cycles or just use one road grade profile with both 

cruise cycles?

EPA Draft Analysis
Other Test Plan on Road Grade Evaluations

• Cummins ISB engine and Allison transmission at SwRI

• Navistar N13 engine with Eaton transmission at SwRI

• Cummins ISX engine and Eaton transmission at ORNL

EPA Draft Analysis
Extra Slides

EPA Draft Analysis
Axle Ratio 2.4, Proposed Profile – 65mph

EPA Draft Analysis
55 mph Cycles - % Difference from Proposed 

Cycle

6.7%

8.4% 8.5%

11.0%

7.7%

5.9%

6.8%

7.5%

9.6%

6.0%

5.1%

6.7% 6.3%

8.6%

5.7%

A - Fwd A - Rvrs B - Fwd B - Rvrs D

Fuel (g/mile)

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

1.2% 1.2%

1.5%

1.0%

1.2%

0.1%

-0.5%

0.5%

-0.5% -0.4%

0.0%

-0.8%

-0.1%

-0.7%

-0.3%

A - Fwd A - Rvrs B - Fwd B - Rvrs D

Fuel (g/kW-hr)

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

EPA Draft Analysis
65 mph Cycles - % Difference from Proposed 

Cycle

5.8%

7.6%

5.5%

6.2% 6.1%

4.0%

5.5%

3.4%

4.5% 4.6%

3.1%

4.0%

2.8%

3.6%

3.3%

A - Fwd A - Rvrs C - Fwd C - Rvrs D

Fuel (g/mile)

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

1.3%

1.1% 1.1%

0.9% 0.9%

0.1%

-0.2%

-0.4%

-0.1% -0.2%

-0.9% -0.9%

-0.4%

-0.2%

-0.9%

A - Fwd A - Rvrs C - Fwd C - Rvrs D

Fuel (g/kW-hr)

Axle Ratio: 2.4 Axle Ratio: 2.64 Axle Ratio: 3.36

EPA Draft Analysis