ALERT-C协议旨在提供主要面向事件的道路最终用户信息。 本文件规定了根据一系列一般要求向用户呈现的信息。它定义了消息结构和内容，以及它对最终用户的表示。 本文档的消息管理组件描述了RDS-TMC的消息管理功能。ALERT-C协议区分用户消息和系统消息。如第5条所定义，用户信息是最终用户可能知道的信息。系统消息仅用于RDS-TMC终端，用于消息管理目的。 RDS-TMC信息包括这两个方面？“系统信息”和？“用户消息”。系统信息与TMC服务相关，并详细说明终端需要能够找到、识别和解码TMC信息的参数。 系统信息以3A型组和8A型组传输。 用户消息包含交通事件的详细信息；这些可能使用一个或多个8A型组。大多数消息可以使用单个8A类型组传输，但是更详细的消息（例如转移建议）最多可以使用五个8A类型组。 本文档的传输组件通过空中传输信息。RDS-TMC使用的ALERT-C协议的基本方法是将大多数消息完全编码在单个RDS组中。 包含所有事件描述的ALERT-C事件列表如ISO 14819-2所述。

The ALERT-C protocol is designed to provide mostly event-oriented road end-user information messages. This document specifies the messages which are presented to the user in accordance with a set of general requirements. It defines the message structure and content and its presentation to the end-user. The message management component of this document describes the message management functions of RDS-TMC. The ALERT-C protocol distinguishes between user messages and system messages. User messages are those potentially made known to the end-user, as defined in Clause 5. System messages are of use only to the RDS-TMC terminal, for message management purposes. RDS-TMC information comprises both?system information' and?user messages'. System information relates to the TMC service and details the parameters that the terminal needs to be able to find, identify and decode the TMC information. System information is transmitted in type 3A groups and in type 8A groups. User messages contain the details of the traffic events; these may use one or more type 8A groups. Most messages may be transmitted using a single type 8A group, however messages with more detail (e.g. diversion advice) may use up to a total of five, type 8A groups. The transmission component of this document conveys the messages over-air. The ALERT-C protocol, used by RDS-TMC, has the fundamental approach of aiming to code most messages entirely within a single RDS group. The ALERT-C Event List, which contains all event descriptions, is described in ISO 14819？2.