Answers to questions on separate technical unit approvals under UN R155 clarify that a base vehicle must already hold an R155 type approval before an ESA can be added at Part III; approval authorities for different parts may differ with mutual recognition applying; the end of support period for an ESA manufacturer must be communicated to the vehicle manufacturer, with implications to be discussed by the IWG; installation of ESAs must follow vehicle manufacturer instructions without necessarily requiring separate agreement; STU data sharing agreements are required; and after ESA installation, a whole vehicle cyber security risk assessment is not necessary, though Part III must consider risks where ESA and base vehicle interactions occur. A working document is planned for submission to GRVA in January 2027. The IWG will explore whether Part II components may include equipment from certificated base vehicles under UN R155 multi-stage categorization and discuss incorporating STU into original approvals.