UN R13 allows for the exemption of certain vehicles from the requirement for electronic stability controls. This proposal seeks to clarify the scope of the exemptions to include any special purpose vehicle with a non-standard chassis. The change was prompted by a modified vehicle where use of ESC was not feasible, but where the current UN R13 language left doubt as to whether the ESC requirement was applicable. This revised proposal takes into account comments received during the February 2016 GRRF session.