AASHTO GSGLC-5:2016 AASHTO Guidelines for Supplemental Guide Signing.
In accordance with the MUTCD, not more than one supplemental guide sign should he provided for a single interchange in each direction along any freeway. No more than two traffic generators should be listed on a supplemental guide sign. \Vhen used, supplemental guide signs should he located in advance of’ the interchanging road that provides the most direct route to the facility.
Supplemental guide signs can be used to information regarding destinations accessible from an interchange, other than places displayed on the standard interchange signing; however, they should only be used in the context of providing a service to the motorist. As there are often far more traffic generators accessible from an interchange than can reasonably be accommodated on directional signage, it is imperative that states establish criteria that limits signage to the most significant generators. Otherwise, the result can be an assortment of directional signage that, while serving the interest of a destination, provides a disservice to the motorist.
General signing criteria and limitations should be established by the states. Only those generators that have the greatest traffic should be considered for display on supplemental guide signs. This does not mean that all facilities that meet the criteria should automatically receive supplemental guide signing. Signing for traffic generators is considered optional and supplemental to the overall signing system for freeways and expressways. Therefore, before a sign fbi’ a traffic generator is installed, sufficient space, as proilel in the MUTUD, should exist to accommodate the J)1cen1ent of the sign without interfering or conflicting with required signing or other optional signing that might be in place. Supplemental guide signs for traffic generators should not be installed at freeway—to—freeway interchanges.
When used, a supplemental guide sign that displays information relating to a traffic generator shotild be located in advance of the freeway exit providing the most direct route to the facility. Consideration may be given to installing a supplemental guide sign on a second freeway when the prime criterion is exceeded by at least 50 Dercetlt and the traffic generator is within two—thirds of the specified distance for the closer freeway and within the specifie(l distance for the further freeway. Supplemental guide signs should not be erected fbi- a traffic generator that would require a motorist to travel on the interchanging road beyond a second freewa)
Signing for a seasonal generator may be displayed when warranted. Such signing should be removed or covered at the end of’ the season, or a changeable message sign or similar device may be used.
Two traffic generators may be displayed on a single, permanent or seasOnal supplemental guide sign. When more than two traffic generators meet the signing criteria, only those generators having the greatest need for signing should be considered for display on a supplemental guide sign. Permanent supplemental guide sign and seasonal supplemental guide sign information for traffic generators may he installed on the same supports.
A supplemental guide sign for a traffic generator shot.ild not be displayed until signing has been installed at the ramp terminals and along the interchanging road and the other roads as necessary to direct the motorist from the freeway to the traffic generator.AASHTO GSGLC-5 pdf download.