The Taihu Bridge connects Xishan Island with the 'mainland' and is part of the X206 highway. Actually it is three bridges, as it uses two smaller islets over its ~7km stretch as hubs to connect to Xishan.
Cycling over the bridge is on a bike lane, not a separate bike path. Better stay in lane, as cars tend to go pretty fast. As Xishan is a popular tourist spot, traffic can be busy on the weekends after 10am. Better go early ;-)