33 CFR § 117.957 - Cedar Bayou.
The draw of the Union Pacific railroad automated bridge, mile 7.0 at Baytown, operates as follows:
(a) The draw shall be maintained at a vertical clearance of 81.4 feet above mean high water. Fixed green navigation lights shall be displayed in the center of the draw.
(b) When a train approaches the bridge, the navigation lights shall be changed from green to red, alternating flashing red lights turned on, and a horn sounded for six minutes. At the end of six minutes, the draw may be lowered and locked if the scanning equipment does not detect any object under the span. If the scanning equipment detects an obstruction, the draw shall be raised until the obstruction is cleared.
(c) After a train has cleared the bridge, the draw shall be raised to 81.4 feet above mean high water, the flashing red lights stopped, and the navigation lights changed from red to green.