Introduction: Road bends of extra-urban and rural roads are known to be particularly relevant for motorcycle riding safety. For this reason a Curve Warning system has been developed for assisting the motorcyclists to safely approach bends and curves. System Description: The system is organized in three layers: the first is the scenario detection that uses on-board sensors and digital maps to feed the second layer, which is the risk assessment layer. This second layer combines road geometry, motorcycle dynamics, and rider style in a holistic approach for computing a safe reference maneuver and for detecting potential dangers in the curve negotiation. The safe reference maneuver is continuously recalculated to follow the evolving scenario according to a receding horizon approach. In case of potential danger, the third layer warns the rider by a proper Human Machine Interface, leaving to the rider the vehicle control. Paper contents: This paper explains the Curve Warning concept and illustrates its implementation, development, and tuning on a motorcycle prototype. The latter has been used for a pilot campaign of road tests, which demonstrated that the system is capable of early detection of potential danger situations, and that riders have a positive attitude towards the Curve Warning system itself.