Function and Purpose：

1. Category B signs are installed on the upstream side of the bridge's main beams (or arches) and are applicable to all bridges.  
2. When placed on both upstream sides of the bridge's main beams (or arches), the left, middle, and right sections of the sign should be used simultaneously.  
3. The centerline of the middle section of the sign should align with the projection of the channel centerline on the upstream side of the main beam or arch.
4. The bottom edge of the middle section of the sign should be level with the bottom of the main beam or the top of the arch. The left and right sections don’t have to be at the same height as the middle section, but the spacing should be the same. 
5. The left and right sections should indicate either the upper width of the navigable clearance, the navigable clearance width, or the current bottom width of the channel.

Main Features：

Sign Boards

1. The sign board is made from aluminum alloy plates or light-colored synthetic resin boards (such as high-strength plastic, polyethylene, or fiberglass panels). The thickness of aluminum alloy plates should be no less than 2mm, and the thickness of synthetic resin boards should be at least twice that of aluminum alloy plates.
2. Sign boards can have folded edges to increase strength, but this should not reduce the overall dimensions of the sign.
3. To ensure quality and make transportation and installation easier, large sign boards should preferably be assembled on-site.

Sign Face

1. The base color of signs should use reflective materials of grade 3 or above, and their performance should comply with the requirements specified in GB5768.2-2009, section 3.11.2.1.
2. For splicing the reflective materials of the sign's base color, mechanically pressed pieces can be joined edge to edge, while manually pressed pieces should overlap.
3. The sign's borders, graphics, symbols, and text can use reflective materials of different grades from the base color.
4. The design of the sign should be enlarged according to the patterns in this document without any arbitrary modifications.

Technical Parameters: