A suspension bridge shows economical priority in ultra-long span. However there are not a few cases that a suspension bridge is adopted in span of less than 1000m from the viewpoint of the local condition or landscape. It is an important subject to reconsider the cable safety factor for suspension bridges, because reduction of the construction cost is a strong requirement. In this paper we design some middle single-span suspension bridges, and calculated the random live loads under traffic congestion by Monte Carlo simulation. We arrived at the conclusion that the reduction of the cable safety factor for middle-span suspension bridges is possible using load factor design method.
