Although expensive, stayed bridges may be the only viable alternative when: there is no access to the gap, on which temporary or permanent piers could be built; when there is no staright level run up to the gap which would permit cantilever launching; when the span is too big for regular through truss bridges. And, in particular, one-tower bridges are useful if there is no good access to the far bank, as they can be built from one side only. But please note: you stll need enough space for the large counterweights, which may need to be one fifth of the spann for a two tower bridge.