California Air Resources Board (CARB)
CFD Testing

Get your aero devices tested by the Team that sets the standard in CFD modeling of Trucks

Having decades of experience in applying Computational Fluid Dynamics (CFD) to determine the aerodynamic performance of automotive vehicles and trucks, for brands like Honda or NASCAR, and as active members of the professional body that sets the industry standards, we are able to apply our expertise to conduct CFD testing on trucks or aero devices to ensure they meet greenhouse emissions (GHG) standards.


As of 2019, changes to the California Air Resources Board (CARB) Tractor-Trailer Greenhouse Gas (TTGHG) Interim Aero Device Approval Program now allows CFD to be used to measure the CdA of your aero devices instead of wind-tunnel testing or coast down. Approval from CARB not to wind-tunnel test is required in advance.

Applying CFD will give fleet operations the potential to speed up the testing process and make it much cheaper and easier, with less burden on the fleet operators to have to take their trucks off the road for physical wind-tunnel testing.

To simplify the testing procedure, TotalSim has automated the CFD process and developed a web-based application for performing highly accurate computational fluid dynamic (CFD) simulations of add-on aerodynamic devices for semi trucks, such as skirts, boat tails and VGs.

Our Simple CFD Process for Testing

To efficiently and quickly determine if your vehicle or aerodynamic devices meet the CARB testing standards, please see below to learn more about the process. We guarantee our CFD methodology will meet the CARB testing standards.
What your testing will be measured against:

  • Your device will be tested on a Standard Truck and Trailer that meets the CARB geometry requirements (outlined in 40 CFR 1037.501(g)(1) and 40 CFR 1037.501(h))
  • CdA improvements will be measured in accordance with CARB CFD Protocols and the SAE J2966 CFD test procedure
  • The Mobile Source Control Division Tractor Trailer Greenhouse Gas Interim Approval Request Form for Aero Drag Reduction Technologies is automatically populated with all the required testing information ready for you to submit to CARB for approval


Whether you have CAD or not, we will help you get your aero device tested via CFD simulation.


TotalSim gets the CFD simulation results from the aero device and we incorporate the data and any supporting documents into the CARB Application as a formal submission to CARB to request approval of your device.

TotalSim will work directly with CARB on your behalf as the CARB staff reviews the submitted application to determine whether your technologies meet the applicable requirements.


Once your device is identified as an approved aerodynamic technology by CARB, we’ll add it to our own database of approved devices to allow more fleets to utilize your device.

TotalSim Total Vehicle CdA with Yaw Angle


TotalSim’s work with SAE for the Trucking Industry

Our own Co-founder and Technical Director, Naethan Eagles, has helped shape the procedures the trucking industry has adopted. Naethan serves on three Society of Automotive Engineers (SAE) Committees which focus on everything from fuel economy to road vehicles to automated and connected commercial vehicles.

Society of Automotive Engineers (SAE) Committees

  • Truck and Bus Aerodynamics and Fuel Economy Committee (member since 2011)
  • Road Vehicle Aerodynamics Forum Committee (member since 2015)
  • Automated and Connected Commercial Vehicle Committee (member since 2017)

Taskforce membership (writing and updating standards)

  • J2966 Taskforce member 2012-2013 “Guidelines for Aerodynamic Assessment of Medium and Heavy Commercial Ground Vehicles Using Computational Fluid Dynamics”
  • J3015 Taskforce member 2013-2016 “Reynolds Number Scaling and Simulation Guidelines and Methods”
  • J1252 Taskforce member 2017-2018 “SAE Wind Tunnel Test Procedure for Trucks and Buses”
  • J3147 Taskforce member 2017-2019 “Evaluation Method Types”
  • J3148 Taskforce member 2017-2019 “Operational Efficiency”

Conference Activity

  • COMVEC 2011: Paper and presentation: 2011-01-2283 “Drag Reduction of a Modern Straight Truck” Author M Cragun
  • COMVEC 2013: Paper and presentation: 2013-01-2415 “A Parametric Assessment of Skirt Performance on a Single Bogie Commercial Vehicle” Author N Eagles
  • COMVEC 2014: Member of “Chat with Expert” Panel
  • COMVEC 2016: Aero Plenary “Shedding Light on CFD”

Journal Publications

  • (13CVA-0003 – A Parametric Assessment of Skirt Performance on a Single Bogie Commercial Vehicle) was been approved for publication in conjunction with session CVA200 – Commercial Vehicle Aerodynamics – Design and Evaluation Process

What is CARB?

Since 2006, Assembly Bill 32, requires California to reduce Greenhouse (GHG) emissions from mobile sources like trucks and therefore the California Air Resources Board (CARB) adopted the Tractor-Trailer Greenhouse Gas (TTGHG) regulation. TTGHG requires the reduction of GHG from heavy-duty tractors that pull 53-foot or longer box-type trailers on California highways and requires the use of more fuel efficient and aerodynamic equipment. This means that anyone driving a heavy-duty tractor or trailer in or out of California beginning in January 2020 must make sure their aero devices meet the TTGHG regulations or be subject to penalty by CARB.

For those looking to certify their devices to be compliant with CARB, the TTGHG Interim Aero Device Approval Program now allows Computational Fluid Dynamics (CFD) to be used to measure the CdA of your Aero Devices instead of wind-tunnel  testing or coast down (approval from CARB not to wind tunnel test is required in advance). The TTGHG Interim Aero Device Approval Program will allow aerodynamic device manufacturers to obtain a preliminary approval for the measured performance of aerodynamic drag reduction technologies, or combinations of technologies, in accordance with the provisions of 40 CFR 1037.2111.

CARB will soon be allowing aerodynamic device manufacturers to submit requests for approval of their devices. CARB staff will review the submitted test results and supporting documents on aerodynamic drag reduction technologies and determine whether the technologies meet the applicable requirements. CARB will issue a written approval for such devices that demonstrate TTGHG compliance. The aerodynamic drag technology will then we identified as an approved aerodynamic technology on CARB’s website and will be eligible for use complying with the TTGHG regulation.