Matthew Rodriquez Secretary for Environmental Protection April27, 2015
Mr. Arvon Mitcham 

# Air Resources Board Mary D . Nichols, Chairman

9480 Telstar Avenue , Suite 4 E l Monte , Californ ia 9 1 731 • www.a rb .ca.gov

Program Manager/Engineer, Light-Duty Vehicle and Small Engine Center United States Environmental Protection Agency 2000 Traverwood Drive Ann Arbor, Michigan 48105 Dear Mr. Mitcham : Edmund G . Brown Jr. Governor

I am writing to respond to U .S. Environmental Protection Agency' s (U.S . EPA) request for information about Air Resources Board 's (ARB) planned pup trailer aerodynamic testing . To support the Phase 2 heavy-duty greenhouse gas rulemaking , ARB added funds to an existing agreement (Agreement Number 11-600) with th e National Renewable En e rgy Laboratory (NREL) (Contract Number FIA- 11-1763) so that NREL could perform a series of tests to explore the potential benefits of using aerodynamic improvement devices on "twin pup" trailers in combination with a class 8 diesel powered tractor. Upon completion of the project, the results will be provided to U .S. EPA and the National Highway Traffic Safety Administration for potential inclusion in the Phase 2 rulemaking. Background Various aerodynamic improvement technologies have been eval uated through the U .S. EPA's SmartWay program . The majority of these technologi es have focused on devices intended for heavy-duty class 8 tractor-trailers in a standard single trailer (48-foot or 53- foot) configuration. It is the intention of this NREL project to complement previous work and explore the potential benefits of using aerodynamic imp rovement devices on a long combination vehicl e, more specifically 28. 5-foot "twin pup " trailers . Summary of NREL Test Project Planned testing will utilize a class 8 diesel powered tractor in combination with a set of 28 .5-foot "twin pup " trail ers. The aerodynamic improvement devices to be tested in clude trailer side skirts and a rear tail fairing. Below is a list of configurations to be tested : • Baseline : tractor, two pups, no aerodynamic improve ment devices; The energy chall enge facing California is real. Every Californian needs t o take immediate action to reduce energy consumption. For a li st ofsimple ways you can reduce demand and cut your energy costs, see our website: http :// www.arb.ca .gov. Ca liforni a Environme ntal Protection Agency Printed on Recycled PaperMr. Arvon Mitcham April27, 2015 Page 2 • Trailer side skirts on the front trailer only ; • Trailer side skirts on the rear trailer only; • Trailer side skirts on both trailers ; and • Trailer side skirts on both trailers and an advanced trailer tail on rear trailer only. All testing will include an appropriate vehicle warm-up period in order to bring the engine, transmission , rear differential and bearing temperatures up to their normal operating range . The test vehicle will be instrumented with data recording devices capable of logging J1939 CAN parameters of interest and a global positioning system to record speed and position at a minimum of 5-Hertz . Testing is tentatively scheduled to begin mid -May 2015 and continue through the end of June 2015. We expect the testing to be completed as scheduled but delays are possible depending on vehicle/trailer rental lead times and weather conditions. If you have questions or need additional information , please contact Ms . Kim HeroyRogalski, Manager, at (916) 327-2200 , or email at kheroyro@arb
.ca .gov or me at (626) 575-6632, or email at mcarter@arb.ca
.gov.

Michael Carter, Chief Mobile Source Regulatory Development Branch California Air Resources Board
cc: Kim Heroy-Rogalski , Manager Strategic Planning & Development Section