Section 2: Sign and Substrate Structure
Anchor: #i1016058Substrate
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 Compliant Work Zone Traffic Control Devices list.
Anchor: #i1016363Structural Support System
Some signs also require a structural support system. The Traffic Engineering Standard Sheets detail the types of materials, thicknesses, support systems, and various other details. Standard Specifications for Construction and Maintenance of Highways, Streets, and Bridges contains specifications to be used in contracts.
Anchor: #i1016783Overhead 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 Traffic Engineering Standard Sheets.
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.