From episode #202, The Case of the Arrogant Arsonist
The Vincent
Thomas Bridge. Hanging below the bridge is safety netting
used
during construction. It's not clear if the bridge was open at
this time or not.
A view on opening day, 15 November 1963. Note that the netting is
still there.
Episode #202 was broadcast on 5 March 1964. That's Fireboat #2
in action.
Picture borrowed from lafire.com.
And here's Fireboat #2 in the bridge scene.