Section 2: Sign and Substrate Structure

Substrate

The sign substrate provides the rigid structural backing and shape for the sign. The substrate must be rigid enough to prevent the sign from flexing or waving in the wind or warping in the sun.
Common substrate materials are flat-sheet aluminum and extruded aluminum. Other substrate materials, such as plywood, roll-up and lightweight materials, may be used in work zones as per the list.

Structural Support System

Some signs also require a structural support system. The detail the types of materials, thicknesses, support systems, and various other details. contains specifications to be used in contracts.

Overhead Sign Walkways

Overhead sign walkways are designed so that maintenance personnel can easily work on dynamic message signs. The walkways provide easy access all along the bridge. Details regarding sign walkways are provided in the .
Overhead sign walkways are optional, since needs may vary from location to location within the district. Factors to consider are traffic conditions, anticipated maintenance, and maintenance equipment available. Some dynamic message signs are manufactured so maintenance personnel can walk inside the sign to perform basic maintenance. A separate sign walkway is not needed on these types of signs.
See Chapter 4 for information on overhead sign maintenance.