AASHTO GSGLC-5, Guidelines for Supplemental Guide Signing, Fifth Edition (2016), addresses the selection and display of supplemental guide signs on freeways, expressways, and Interstate highways. Part 1 gives guidelines for selecting supplemental guide signs for traffic generators adjacent to freeways, and Part 2 covers airport guide signing. Part 3 provides a list of control cities for use in guide signs on Interstate highways. The guidelines are intended to help state departments of transportation and other transportation agencies choose appropriate traffic generators for display and to develop individual state policies that reflect local needs, customs, and legal requirements. Agencies may use the three parts together or draw on the one that matches a particular signing question. The document is written for traffic engineers and signing specialists responsible for guide sign policy and design.