PORTLAND — Transportation planners have established special signs on the Martin’s Point Bridge directing motorists to share the roadway during a more than year-long process to replace the route-1 span. Cyclists are welcomed to use a temporary sidewalk, too. Completion of the project, including removal of the more than 60-year-old structure is expected in early 2014, but the new bridge is likely to open earlier. When finished, the new roadway will have ample shoulders and sidewalks for all forms of non-automotive transport, said Paul Niehoff, senior transportation planner at the Portland Area Comprehensive Transportation System, a regional planning organization.