Abstract
To prevent collision accidents in case of the excavator operation, adequate warning methods are considered to the operator and workers near the machine. This method has two features compared with conventional collision prevention devices. Firstly, it has "Mental Hazardous Area" in additional with "Physical Hazardous Area". Workers feel danger in this "Mental Hazardous Area", though no collision occurs physically. Secondly, it is possible to modify these two areas freely in accordance with its work type. "Mental Hazardous Area" is measured by using Virtual Reality room named "CAVE". Ten professional operators have done one construction experiment so as to check this warning method functions.
