Due to the dynamic environment in which cable-stayed bridges work, sudden failure of stay cables are likely to happen for diverse reasons. The more rapid is the failure the more severe will be the effect on the bridge, risking not just the breakage of one or more elements due to a zipper-type collapse, but of the whole system. The impact of a vehicle is the event that most likely is able to produce such a consequence and the regulations only consider a possible loss of just one element. For this reason in the following study the impact of a heavy vehicle is considered in order to see how a single cable would respond or how a system of cables would respond, if more than one is affected.