ABSTRACT
A double-exponential probability distribution function (DEPDF) is introduced to quantify the likelihood of the human failure to perform his/her duties, when operating a vehicle: an aircraft, a spacecraft, a boat, a helicopter, a car, and so on. Such a failure, if any, is attributed in our approach to the insufficient human capacity factor (HCF), when there is a need to cope with a high (extraordinary, off-normal) level mental workload (MWL). The MWL depends on the operational conditions and the complexity of the mission. The MWL is directly affected by the challenges that a navigator faces, when he/she has to control the vehicle in a complex, heterogeneous, multitask, and often uncertain and harsh environment. Such an environment includes numerous different and interrelated concepts of situational awareness: spatial awareness for instrument displays; system awareness; and task awareness that has to do with attention and task management.
