Iowa DOT using audible attenuators to increase short-term work zone awareness Attenuators designed to warn drivers of crews ahead and take the crash impact if drivers do not slow down or move over April 30, 2021 / 2 minute read Image: Iowa DOT The Iowa Department of Transportation is employing a number of safety practices including the use of audible attenuators on short-term, stationary, or slow-moving maintenance operations. The attenuators are designed to warn drivers of crews ahead and take the impact of a crash if a driver does not slow down or move over for the crew. An attenuator is a trailer that is pulled behind a truck equipped with flashing lights and signage signaling the presence of crews. If a driver does not appear to slow down or move over for the crew, the attenuator operator has the ability to turn on additional flashing lights that shine at a higher frequency. If a driver is still not responding to the extra lighting, the attenuator operator can then activate an audible sound in a final attempt to get the attention of the driver.