Originally Posted by RJay
Yes, I'm sure they differ from state to state. Another sign used is No Jake Brakes.
Most of the signs that I've seen say "Engine Brake" . By definition, this is NOT an exhaust brake. I can hear no difference in our engine between a downshift and a downshift with the exhaust brake so I would never expect to be challenged by local authorities. As indicated in other posts, I believe they are trying to regulate the unmuffled brakes which actually use engine compression rather than a butterfly valve in the exhaust to create a braking effect.
Many more modern trucks have added muffler systems to the output of the engine brakes. I've never done a side by side comparison of the muffled versus the unmuffled so I don't know if those mufflers would allow a greater use of the engine brakes in towns with prohbitions.
The sign that I pay attention to is axle weight limits. While we are no where near what truck axles weigh, there are some roads with very low limits and we would be in violation of those limits with our rear axle.