The draw of the Union Pacific railroad bridge, mile 20.7 near Brazoria, shall open on signal; except that, from 10 a.m. to 2 p.m. and 10 p.m. to 2 a.m., the draw shall open on signal if at least three hours notice is given. [CGD 08-84-14, 50 FR 15743, Apr. 22, 1985]