The two swing bridges and their timber trestle approaches were known to be in poor shape since 1996,[REF] and a subsequent 2008 engineering investigation found the concrete foundations were also degraded, possibly since they were constructed in 1910 [REF].
The existing two-track Dumbarton Cut-off line would be converted to a single track system with centralized traffic control; the second track would be retained as a siding in certain portions.