Factors which drive the design process are many and varied.... Elements from existing or planned architectural and/or hardscape features may be incorporated to make the wayfinding components feel like they belong; that they are part of the overall plan. Issues that affect the appearance and function of the design include those relating to traffic flow and human factors, such as sight lines, viewing distances, and psychological responses to colors, contrast and images. An initial programming exercise reveals verbiage and graphical image requirements, which, along with viewing distance requirements, help determine dimensions of individual system components. Practical considerations relating to codes, such as those dictated by the Department of Transportation and the ADA (Americans with Disabilities Act) also drive the design and placement of signage and wayfinding components. Energy consumption by powered signs, directories, and information kiosks, becomes an important issue relating to achieving LEED (Leadership in Energy and Environmental Design) certification. Designers also are finding more and more sustainably produced materials available for fabrication and implementation of their designs.