Can we keep using our older metal Work Zone signs?
If a sign and sign support combination is crash-worthy, you can keep using it.
Many older portable sign supports are not crash worthy. In an accident, the sign or support may become a flying hazard or may cause too much damage when a small vehicle strikes it. In order to be used, the sign either needs to have been crash tested or self-certified by the vendor. Detailed information on both can be found on the FHWA website.
The only self-certified traffic control devices are cones, barrels, and delineators with good history in the field. Metal signs on portable stands do NOT fall into this category and must be crash tested. The FHWA has a website listing all of the crash tested hardware (see the links below). If your sign is not on the list, then you should look into newer supports. The requirement for crashworthiness went into effect January 17, 2005.
There is more information about mounting signs other than on posts, on the National MUTCD website.