This document provides terminology and general guidance on the principles of collision warning and collision avoidance systems for:— earth moving machinery as defined in ISO 6165,— mobile underground mining machinery as defined in ISO 19296, and— road construction machinery as defined in ISO 22242.This document provides general requirements for detection of objects, warnings to the operator, automatic intervention control to avoid collision, and test procedures. It is intended to be used in conjunction with the other parts of the ISO 21815 series, which provide detailed guidance and requirements for collision warning and collision avoidance systems and determining risk areas and risk levels. The specific requirements and definitions for particular types of machines are defined in the use case parts of the ISO 21815 series.This document covers collision avoidance by speed reduction or motion inhibit: it does not cover avoidance by automatic manoeuvring (e.g. steering) away from the intended object.The systems described in this document are only intended to assist the operator of the machine. The responsibility for safe operation of the machine remains with the operator of the machine.This document is not applicable to collision warning and collision avoidance systems installed to the machine before the date of its publication.