Method of rebuilding a viaduct without interrupting service on the old structure

A method of launching spans of a new viaduct erected above an old viaduct beyond the ends of said old viaduct without interrupting service on the old viaduct as a means to lengthen the viaduct or to launch a roadbed transition ramp to lower or to raise the said new viaduct roadbed path to the roadbed continuing beyond the old viaduct roadbed, comprising the steps of:

• a) placing additional subassemblies sufficient to assemble approximately 3 spans atop said new viaduct also atop an array of wheelsets or air cushion pallets interspersed between the new viaduct roadbed and said subassemblies,
• b) transporting said spans to an end of the new viaduct,
• c) erecting a cablestay mast centered upon a central span directly behind the far end span of the transported spans,
• d) arraying cablestays along the length of the said far end span and along the rear span,
• e) tensioning said cablestays to put the two end spans in suspension,
• f) moving the assembled cablestays, mast and spans one span length beyond the end of the new roadbed putting the far end suspended span in cantilever,
• g) lowering the far span with tall supporting jacks into level alignment with the new viaduct roadbed,
• h) repeating the process as often as necessary while the extended spans are level, and
• i) creating said transition ramp of requisite length by raising or lowering the far end of the transition ramp with said tall supporting jacks and erecting supporting columns or columns and span supporting beams to replace all tall jacks.