122 seamanship secrets
Bascule bridges (drawbridges). Th ese drawbridges have one or two arms—
called leafs—on hinges. Single-arm bascules have much less horizontal clearance
than those with two arms. Check the vertical and horizontal clearances before
attempting a passage through this type of bridge. Chart symbols for bascule
bridges do not indicate single or double arm (leafs). Look in the Coast Pilot
(see Chapter 1) or a local Waterways Cruising guide for more detailed clear-
ance information.
Swing bridges. Swing bridges turn on a vertical axis, allowing one-way
traffic on each side. The tall center span acts as a dividing line for the boat
traffic that passes on each side.
Lift bridges. Th ese giant elevator bridges have two monster legs on each side.
Th e center span remains horizontal while moving up and down the legs.
BRIDGE LIGHT INTERPRETATION
Bridges display red, green, or white lights to indicate open and closed positions,
fender locations, and channel edges. Th e descriptions below, along with the illustra-
tions of the light patterns on fi xed and movable bridges, will provide guidance as
you navigate under bridges at nighttime. In general, bridge lighting follows these
rules. In any event, always check the Local Notices to Mariners (see Chapter 1) for
bridge light outages, construction information, or changes to opening schedules.
Red lights. Red lights mark the edges of the passage beneath a bridge. Installed
on fenders or adjacent to the green center span lights, red lights show the width
of the channel under the bridge. If the bridge moves, red lights warn the mariner
to stop. For example, on a bascule bridge with two arms (or leafs), the leaf ends
show a red light when closed; when they are opened, the light changes to green.
On a lift bridge (the bridge moves up and down), wait until the center span light
turns green before passing underneath. (See illustration on page 124.)
Green lights. On fi xed bridges: Two rangelike green lights mark the highest
vertical clearance of the bridge and show the channel centerline. Th ese lights hang
on poles from the top of the highest part of the arc. When in line (range), they help
Fixed-bridge lighting. Fixed bridges with multiple channels illuminate each channel
separately. Th e three white lights are always over the center channel.