# Human Factors Analysis of Air Traffic Safety Based on HFACS-BN Model
## 3 Theoretical Development
### Data Collection  
Generally, when the number of parents involved in a BN is large, collecting a conditional probability table (CPT) of each node from the accident/incident reports or experts' opinions is a challenging task. Since the accident reports related to ATC cannot record all the information of each node, it is difficult to deduce CPTs directly from the database. In this paper, the original parameters of CPT are obtained \begin{table}
\begin{tabular}{p{142.3 pt} p{142.3 pt} p{142.3 pt}} \hline \hline
**Factors** & **HFACS Level** & **Description** & **Source** \\ \hline Safety Culture & & It includes the safety policy of the ATC department, safety education, as well as preventive measures & CAA (2003) [35] \\ Team Human & & The duty of the team members is not clear, the collocation resource Allocation & [PERSON] [33] \\ Salary and Reward & Organizational Influence & It refers to salary and workload that do not match, employees that are not satisfied with the salary and reward & CAA (2002a) [35] \\ ATC Communication & & Communication between controllers, including briefing on handover & [PERSON] [36] \\ ATC/Flight & & It refers to the communication and coordination between ATCOs and crew members & SKYbrary [37] \\ Crew Cooperation & & It includes ATC equipment layout, hardware failure, software interaction and so on & SKYbrary [37] \\ \hline Lack of Supervision Plan & & ATC supervision is not in place, not comprehensive, not meticulous, etc. & [PERSON] [33] \\ Poor Management & & It means the management style discipline/supervision effect & Experts’ opinions \\ Discipline & & It leads to an inadequate understanding of the rules by air regulations & [PERSON] [6] \\ Failed to Enforce & & traffic controllers and may raise safety risks & [PERSON] [33] \\ Regulations & & It occurs when ATCO does not correct unsafe acts & ICAO [38] \\ Failed to Correct & & It considers monitoring flight path, aircraft systems, operational factors, crew/situational awareness. & ICAO [38] \\ \hline Visibility & & Poor visibility due to weather or environmental conditions, unable to effectively monitor aircraft status & SKYbrary [37] \\ Air-Ground & & Ground–to–air communication frequency is seriously disturbed by the external environment & Experts’ opinions \\ Communication & & Mental, emotional or physical tension, strain or distress & [PERSON] [33] \\ Interference & Preconditions for Unsafe Acts & It includes ambient nose from air traffic controllers, noise from crew members, or other noises in the radio & Experts’ opinions \\ Training & & Lack of training materials or inadequate training & [PERSON] [34] \\ Physical Fatigue & & Factors related to a lack of sleep or long work days & IATA (2006) \\ \hline Nonstandard Flight & & Aircraft call number, departure location, aircraft model and other information are not standard & SKYbrary [37] \\ Progress Strip & & Distraction refers to the lack of concentration of air traffic controllers, which affects the normal work of ATC & [PERSON] [35] \\ Distraction & & It refers to the use of informal terms in air traffic control activities & SKYbrary [37] \\ Use Non-standard Terms & & There are two types: intended clearance given to wrong aircraft or wrong clearance given to intended aircraft & SKYbrary [37] \\ ATC clearance error & & ATCO do not have a good command of special situation handling procedures, poor psychological endurance & ICAO [38] \\ Emergency Mishandling & & Mis operation or decision-making by the ATCO in the control process & [PERSON] [33] \\ Operation/Decision Error & & It refers to careless, absent-minded, insincere control work, resulting in instruction errors & ICAO [38] \\ \multirow{2}{*}{ATCO Misspeaking} & & & \\ Procedural & Not following procedures: FARs, OEM standards, SOPs; Noncompliance & It always results in a greater risk for the operation & SKYbrary [37] \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Factors description and its sources. by combining the analysis of aviation accident reports and survey.