NREL is a national laboratory of the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Summary of NREL’s Recent Class 8 

Tractor Trailer Platooning Testing

Mike Lammert, Ken Kelly, and Kevin Walkowicz

21st Century Truck Conference Call

August 19, 2014

NREL/PR-5400-62644
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Project Objective

• Repeatable track testing to assess fuel savings 

potential from semi-automated truck platooning

o Supported by DOE’s Vehicle Technologies Office

o SAE J1321 Type II Fuel Consumption Test Procedure

• Test American-style line haul sleeper cabs with 

modern aerodynamics

o EPA SmartWay tractors; trailers with side skirts

• Test range of following distances, vehicle loadings 

and speeds common in the U.S. (up to 70 mph) 8.5-mile oval at Continental Tire Uvalde 

Proving Grounds (© 2014 Google)

2011 Peterbilt tractors with 53-ft van body trailers

For Illustration Only (Photo courtesy of Peloton, NREL 31236) 
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Platooning System Testing

• Demonstration system provided by Peloton 

Technology, Inc.

• Enabling technologies for platooning

o Forward object detection (radar, laser, stereo 

cameras, etc.)

o Dedication short-range communication (DSRC)

o Vehicle-to-vehicle communications (V2V) and 

driver displays

o Vehicle braking and torque control interface

Test Matrix

Trailing 

Distance

55 mph, 

65,000 lb

65 mph, 

65,000 lb

70 mph, 

65,000 lb

Variable 

Speed, 

65,000 lb

65 mph, 

80,000 lb

20 ft X

30 ft X X X

40 ft X

50 ft X X X X X

75 ft X

• Testing details

o Ten constant speed tests and one variable 

speed test

o 20–75 ft vehicle gaps

 65 mph = 95 ft/s; 6-sec rule of thumb 

would give 570 ft following distance

o Gravimetric fuel measurements with 

weigh tanks

o J1939 data collection, including coolant 

temperature and fan state
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Summary of SAE J1321 Type II Test Procedure

TT/CC rrrrrrrrrr =

TTTTTT vv v vvvv ffff

CC CC vv v vvvv ffff

% IIIIII II =

TT/CC TTTTTT

TT/CC BB

• Warm-up runs ensure all trucks at stable operating temperatures

• Control truck accounts for changes in atmospheric conditions between 

baseline and test runs
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Results: Fuel Savings

Photo courtesy of Peloton 

Technology Inc.

• Team fuel savings ranged from 3.7% to 6.4%

• Closer following distances caused the engine fan on the trailing truck to engage, 

negatively impacting fuel savings
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Fuel Consumption Results: Individual Fuel Savings

• 2.2% to 5.3% savings @ 65,000 lb GVW

• Shorter following distances consistently produced greater fuel savings

(95% CI bars are calculated with SAE J1321 software)
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• Trailing truck demonstrated savings from 2.8% to 9.7%

o Tests with no “fan on” time had savings of 8.4% to 9.7%

o Fan duty cycle as high as 19%

Fuel Consumption Results: Individual Fuel Savings
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Fuel Consumption Results: Team Fuel Savings

• Team fuel savings ranged from 3.7% to 6.4%

o Best combined result was for 55 mph, 30-ft gap, 65,000 lb GVW

• Higher GVW negatively impacted fuel-saved percent

• Percent savings at 70 mph were lower than at 55 mph and 65 mph

Photo courtesy of 

Peloton Technology 

Inc.
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Fuel Economy Results

 Baseline mpg is the test distance of 59.4 miles divided by an average 

of all baseline run fuel-consumption results from both test trucks for 

each speed and load condition 

 Platooning mpg is calculated by applying the SAE procedure 

calculated-percent fuel savings to the baseline fuel consumption 

average

• Platooning improved fuel economy at all speeds and conditions

o Best mpg overall was platooning at 55 mph

• Baseline condition tests show effect of speed on mpg

o 7.82 mpg @ 55 mph

o 6.58 mpg @ 65 mph

o 6.07 mpg @ 70 mph

• Baseline condition tests show effect of mass on mpg

o 6.58 mpg @ 65 mph & 65,000 lb

o 6.33 mpg @ 65 mph & 80,000 lb.
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Fuel Economy Results: Lead Truck MPG
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Fuel Economy Results: Trailing Truck MPG
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Fuel Economy Results: Team MPG
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Platooning Following Distance Error

• Error biased to greater following distance

• Even aggressive variable speed test had minimal encroachment of following 

distance
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Platooning Driver Position Error

• Driver error bias in consistent direction throughout testing

• Increased maximum error at 30’ could have reduced savings and was a test series 

run from 8-12PM after a long test day so fatigue / darkness could be contributing
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Summary of Key Findings

• Significant line-haul fuel savings possible through platooning

o Tests showed fuel savings for the lead (up to 5.3%) and trailing (up to 

9.7%) trucks

o The demonstrated “team” savings of 6.4% could be an attractive return 

on investment for a fleet

• Engine coolant temperature needs to be monitored/addressed 

for the trailing vehicle

o Optimum following distance may depend on ambient temperature and 

vehicle load (absent some aerodynamic aid for radiator air flow)

• Heavy payloads affect the percent improvement from 

platooning, but still result in substantial fuel savings

Full details from present study will be published:

• At SAE COMVEC in October 2014 (paper number 2014-01-2438)

• In an NREL technical report in late 2014
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Potential Future Work

• More data points/test sets to confirm the trends seen here

o Including greater following distances to clarify the optimum configuration

• Incorporate direct aerodynamic study into track testing (truckmounted anemometer, smoke trails, etc.)

• Complementary computational fluid dynamics modeling

• Test platoons of more than two tractor trailer combinations 

• Further analysis including assessments of current line-haul travel

o What percent of national line-haul miles would be conducive to 

platooning?

o How often trucks typically travel together and at what following 

distance?

• Design aerodynamic aids specific to platooning to address the 

loss of cooling airflow over the radiator for the trailing tractor

• Assess any impact of platooning on criteria emissions (e.g., NOx)
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Acknowledgements

This work was supported by the U.S. Department of Energy 

(DOE) Advanced Vehicle Testing Activity through Intertek 

Testing Services, North America, and would not have been 

possible without the generous donation of time and vehicles 

from Peloton, Inc. The authors wish to thank Lee Slezak and 

David Anderson at DOE, and Josh Switkes at Peloton for their 

support.
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