Field devices are a key component in intelligent transport systems (ITS). Field devices include traffic signals, message signs, weather stations, traffic sensors, roadside equipment for connected ITS (C-ITS) environments, etc.Field devices often need to exchange information with other external entities (managers). Field devices can be quite complex, necessitating the standardization of many data concepts for exchange. As such, the ISO 20684 series is divided several individual parts.This document specifies the user needs, requirements and design elements that are used to record timestamped information in a log for later retrieval. This allows a manager to determine the state of a particular object instance nearly simultaneously when the trigger action occurs without frequent polling.NOTE 1 There are similarities between certain portions of NTCIP 1103.NOTE 2 ISO 20684-1 provides additional details about how the ISO 20684 series relates to the overall ITS architecture.