THAMES TIDAL BARRIER

When the Barrier is not closed for flood prevention or training purposes,
vessels may navigate through spans B, C, D, E, F and G in accordance with the
traffic signals exhibited. Traffic through a span is strictly one-way. One or
more spans may be closed for training or maintenance purposes. Spans A, H, J
and K are closed to navigation at all times.

TRAFFIC SIGNALS AT THE BARRIER

Signals indicating the spans to be used for navigation are exhibited from the
piers on either side of each span. Signals are as follows:
        Green arrow - span in use for navigation
        Red cross - span closed to navigation
In low visibility high intensity directional fixed white lights operate
on either side of spans C, D, E and F in conjunction with the green
arrows. Information regarding the spans in use is broadcast by the Thames
Barrier Navigation Centre.
