The Working Party on Lighting and Light-Signalling (GRE) prepares regulatory proposals on light-related vehicle safety systems for consideration by the World Forum/WP.29. The GRE enables more than 70 government, industry, and other interested experts to cooperate in the development of regulatory requirements through joint research and validation of test procedures.

GRE works especially closely with the International Automotive Lighting and Light-signalling Expert Group (more commonly known as the GTB), a global group of vehicle manufacturers, system suppliers, light source manufacturers, testing laboratories and academia working to assure the effective regulation and safety of automotive lighting systems and their installation.

GRE usually convenes in March and October of each year.