Complete demolition is not necessary. Only shortening on the bridge side and extension on the RJY side will be sufficient. During the construction of the bridge, some place was left on the bridge side of PF1 for an approach to the bridge for a second line. If the PF on that end is shortened by a small length, then the new line can curve into PF1 while the current PF2 line can serve as the PF for the existing line on the bridge.