The draw of the CSX Transportation Railroad bridge, mile 0.1 near Saraland, shall open on signal; except that, from 6 p.m. to 10 a.m. the draw shall open on signal if at least eight hours notice is given. During periods of severe storms or hurricanes, from the time the National Weather Service sounds an “alert” for the area until the “all clear” is sounded, the draw shall open on signal.