Effective January 22, 2008, the FHWA introduces new standards in sign reflectivity.
The FHWA expects that the reflectivity levels and maintenance methods will help to promote
safety and mobility on the nation's streets and highways.

- Type I, II and III white sheeting should not be used on overhead guide signs (white on green).
- Type I sheeting should not be used on warning signs (black on yellow/orange).
- Replacement of regulatory, warning, and ground-mounted guide (except street name) within seven years of effective date.
- Replacement of street name signs and overhead guide within ten years of effective date.
- Implementation and continued use of an assessment or management method that is designed to maintain traffic sign retroreflectivity at or above the established minimum levels within four years of effective date.

Visit the FHWA website for complete details and minimum reflectivity tables:
http://safety.fhwa.dot.gov/roadway_dept/retro/index.htm