An attachment assembly and a method for mounting a traffic control device to a mast arm are provided. The attachment assembly includes an attachment device. The attachment device includes a first portion operably connect to the mast arm so that a first surface of the first portion is oriented toward the mast arm, a second portion extending substantially parallel to the first portion along at least a portion of a first length, a second surface of the second portion is oriented toward the traffic control device, and a third portion having a third length and extending between the first portion and the second portion so that a gap is formed between a second face of the first portion and a first face of the second portion that allows the attachment device to flex when the traffic control device is mounted to the mast arm.