This SAE Recommended Practice defines a document for the format of messages and data that is of general value to modules on the data communications link. Included are field descriptions, size, scale, internal data representation, and position within a message. This document also describes guidelines for the frequency of and circumstances in which messages are transmitted. In order to promote compatibility among all aspects of electronic data used in heavy-duty applications, it is the intention of the Data Format Subcommittee (in conjunction with other industry groups) to develop recommended message formats for: a. Vehicle and Component InformationThis includes all information that pertains to the operation of the vehicle and its components (such as performance, maintenance, and diagnostic data). b. Routing and Scheduling InformationInformation related to the planned or actual route of the vehicle. It includes current vehicle location (for example, geographical coordinates) and estimated time of arrival. c. Driver InformationInformation related to driver activity. Includes driver identification, logs, (for example, DOT), driver expenses, performance, status, and payroll data. d. Freight InformationProvides data associated with cargo being shipped, picked up, or delivered. Includes freight status, overage, shortage and damage reporting, billing and invoice information as well as customer and consignee data. This document represents the recommended formats for basic vehicle and component identification and performance data. This document is intended as guide toward standard practice and is subject to change to keep pace with experience and technical advances. Purpose The purpose of this document is to define the format of the messages and data being communicated between microprocessors used in heavy-duty vehicle applications. It is meant to serve as a guide toward a standard practice to promote software compatibility among microcomputer based modules. This document is to be used with SAE J1708. SAE J1708 defines the requirements for the hardware and basic protocol that is needed to implement this document. The primary use of the communications link and message format is expected to be the sharing of data among stand-alone modules. It is anticipated that this document (when used in conjunction with SAE J1708) will reduce the cost and complexity associated with developing and maintaining software for heavy-duty vehicle microprocessor applications.