## 1 Introduction  
In construction and deconstruction works, staff and machinery are exposed to difficult conditions, such as high temperature, ground collapses, landslides, noise, dust, mud, and radioactive contamination. An increasing variety of construction projects carried out over the years, also in wintertime, indicates a demand for the latest technology with maximum process reliability. Apart from difficult working conditions, there is an increasing number of accidents in which operators and people in general are harmed and which result from unskilled machine operation or loss of stability. When operating a machine, experienced operators understand the capabilities of their machine (its maximum tilt, the reach of the arm, etc.) before it loses stability, i.e., tips over because of an unfavorable tilt angle. If the machine is operated in conditions unknown to the operator, there is an increased risk of it exceeding the permissible work limits and thus losing stability. Hence, we increasingly hear about machines overturning unexpectedly, especially excavators--mini diggers. In order to protect the operator from injury in such accidents, protective structures that meet specific requirements are built for machines with an operator cabin or operator seated on the machine. Examples of such structures include Roll-Over Protective Structures (ROPS), which protect the operator in the event of a machine overturning, and Falling Object Protective Structures (FOPS), which protect the operator from falling objects [1; 2; 3]. An example of a mini-excavator with a protective structure is shown in Figure 1a, while Figure 1b shows a remote-controlled demolition robot with the operator standing next to the machine. In the latter case, without the knowledge of the machine's behavior, the operator cannot sense the critical moment before overturning.  
Because they offer the possibility for the operator to be outside the machine, remote-controlled demolition robots are often used in situations where operators are at a higher risk of injury, e.g., building demolitions, toxic environments, areas with the danger of nuclear contamination or places that are difficult to access by the operator, such as narrow silos of a cement plant [4; 5]. On the one hand, this improves the safety of human beings but, on the other hand, it eliminates the possibility for the machine to provide feedback related to the working conditions. This can be compared to what a driver experiences in his or her car, for instance the difference in vibration when driving on different types of surfaces or the momentum of the engine, the spinning of wheels, etc. Just as in the case of the driver who uses such information to drive safely, the operator needs it to operate a heavy machine, such as a demolition robot, without damaging it.  
Figure 2 shows an example of excavator overturning because it exceeded the tilting angle during operation. Figure 2 depicts an excavator that fell onto a pedestrian crossing and hit an accidental passer-by. The protective structure successfully protected the operator but the excessive tilt of the machine during operation contributed to this unfortunate accident.  
A case study of machine overturning accidents as well as the application of the proposed design and construction method based on user research served as the basis for the development of an accident prevention system for heavy duty machines, with special focus on mini-diggers and remote-controlled demolition robots.  
Figure 1: Example of heavy duty machines: (**a**) Mini-digger with operator cabin; (**b**) Remote controlled robot with the operator standing next to the machine.