Jacobs Vehicle Systems has received inquiries regarding engine brake use and noise. The posting of engine brake signs (like the one shown to the right) along the roads and highways of North America has created much controversy with both residents and drivers alike. This page has been established to inform interested parties about engine exhaust noise, and provide the data and information necessary to understand the issue. We hope you find the information on this page useful, and we welcome any feedback. Click here to use our feedback form.

Frequently Asked Questions about Engine Brake Noise
FAQ8: I've seen signs posted that say "No Jake Brakes", what does this mean?
FAQ9: I'm bothered by the noise of big trucks using their Engine Brakes, what can I do?

More information on Engine Exhaust Noise

• Jacobs Engine Exhaust Noise Presentation
  Download Presentation (MS PowerPoint)  |  View Presentation in HTML
• Sample Letter: This is the letter that is sent when we are made aware of a sign specifically prohibiting Jake Brake.
  DOWNLOAD: Sign Notice
• Sample Letter: This is the letter that is sent when we are made aware of an upcoming legislative ordiance that prohibits Jake Brake or engine brake use.
  DOWNLOAD: Ordinance Help
• !! NEW !! 2003 Montana House Bill 237 requiring mufflers on engine brake equipped commercial vehicles, signed April 17, 2003.
  DOWNLOAD: Montana Law
  Link to: Montana Legislature Web Site
• Colorado House Bill 00-1142 requiring mufflers on engine brake equipped commercial vehicles.
  DOWNLOAD: Colorado Bill
• Multi-State Highway Transportation Agreement (MHTA) Update. Model legislation based on the recent law in Colorado requiring commercial vehicles with engine brakes to have proper exhaust mufflers on any truck operating in the state. The MHTA has adopted Colorado's law (with some modification) and it has been brought back to the member states of Arizona, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, and Wyoming.
  DOWNLOAD: MHTA Agreement
• American Association of Motor Vehicle Administrator (AAMVA) web site contains information on the muffler identity and inspection procedures that can be adopted in your state. With this criteria, a commercial vehicle can be inspected for the presence and integrity of an appropriate muffler system. Click here to download the muffler inspection instructions.
• American Trucking Associations, Inc (ATA) Transport Topics Magazine Opinion Editorial, September 19, 2001.
• WHITE PAPER: Vehicle Noise and Compression Release Engine Braking
  ABSTRACT: Engine brakes have been incorrectly identified as a primary source for commercial vehicle noise. This has resulted in an increasing number of "No Engine Brake" signs posted along roadways. Improperly muffled vehicles are the root cause of noise issues concerning communities. Appropriate solutions to the noise issue include inspection of vehicles for the presence of a muffler and the enforcement of existing laws.
  Click here to read the four page paper online
  Click here to download it in Adobe Acrobat PDF.

The following documents from the Society of Automotive Engineers are referenced in the Jaobs technical paper above. These documents are available from SAE and can be ordered on-line from the SAE Web Site by document number for a nominal charge. Click here to go to SAE.

Donaldson Silent Partner^TM Muffler You may have heard about the Silent Partner^TM Muffler from Donaldson Company. This product was developed and tested in conjunction with Jacobs Vehicle Systems. The silent partner is an exhaust silencer designed to further decrease noise produced during both acceleration and engine braking to bring the engine exhaust levels below what they would be with premium mufflers. For those who want the ultimate exhaust noise reduction technology.