Probability based safety concepts are employed in developing a design manual for long-span cablesupported bridges in Korea.In order to offer flexibility to the owners and the designers,the target safety level and the design period are classified for the structures and the structural members.The leading variable loads such as live load,wind load and earthquake are defined in perspective of probability and statistics corresponding to the design periods.The design manual offers the safety factors for the design corresponding to the target safety levels as well as the design periods of the structure and the structural members.