ROADrule USATONS is a quick reference tool that identifies the most common U. S. aids to navigation, rules of the road, and maneuvering and warning signals for U. S. waters. ROADrule takes a large amount of complex information and makes it easy to understand. Whether in a classroom or at the helm, critical decisions can be made quickly and with confidence with the aide of ROADrule. Its design is similar to a slide-rule.