Airside Operations Safety: Understanding the Effects of Human Factors (2022)

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10 Human Factors Defined For airport management to effectively address human factors in airside operations, an under- standing of what is meant by the term “human factors” is required. This chapter addresses what is included under the human factors umbrella. The concept of human factors is defined, and a systematic approach to analyzing the human factors contributing to airport incidents and accidents is presented. After that discussion, two key aspects of human factors frequently found to be at the root of safety incidents are addressed: decision errors and communications. The chapter concludes with a discussion of situational awareness, which is a term that is frequently used in aviation but often without a full understanding of its meaning. Relevant examples are provided to highlight these concepts as they relate to airside operations. 2.1 What Are Human Factors? The term “human factors” has been defined in many ways over the past few decades. Most of the definitions include some explanation of the interaction between humans and tools, machines, systems, or the environment (Stone et al., 2018). When humans interact with tools and machines, an engineer will typically focus on how to improve the tool or machine, while a human factors expert would instead look at the interaction from the viewpoint of the human operator or user. For example, if a human operator is using a new piece of equipment with multiple color displays, human factors experts might focus on how easily and efficiently the human can process the information on the displays. They might analyze how the different colors, labels, warnings, alerts, and so forth are handled by the human visual, auditory, and tactile systems. They would then offer recommendations on how to improve the design of the product to improve safety, efficiency, operator comfort, and other operational factors. Figure 2-1 illustrates subsets of human factors. Human performance focuses on the ability and performance of human operators within the human–machine system (Dekker, 2002). One subset of human performance is human error, where the person makes a mistake either willingly or accidentally (Reason, 1990). Based on the results of the analysis on the V/PD data sets provided by the FAA, it was determined that the primary focus in presenting human factors information to the airport industry was on this subset of human error. The analysis showed that most V/PDs appear to be caused by human error. In the case of V/PDs, which are an important safety issue for airport operators, there are several human factors relationships that could be examined when management addresses airside safety risks. First, the efforts could focus on how the human interacts with various tools C H A P T E R   2 Human factors experts look at how humans interact with tools and machines from the viewpoint of the human operator or user . . . and offer recommen- dations on how to improve the design of the product to improve safety, efficiency, comfort, and other factors.

Human Factors Defined 11   (Parsons, 1999), such as those used during airport operations. These could include hand tools or more complex machine tools (e.g., vehicles used airside, radios installed in airport vehicles). In the case of runway incursions, the data analysis showed that human operators often have difficulty with radio communication; at least in some cases, this is due to improper use of the radios or a lack of awareness that the radios are not operating optimally. This may not be an engineering issue, but rather an issue of the humans not understanding that they are either using the radio improperly or that the radio is not working properly. Either way, the human factor is critical to examine when attempting to mitigate events like these. Second, risk-mitigation efforts could focus on how humans interact with machines, including vehicles, mowing machines, power tools, fuel trucks, baggage machines, and tow tugs. According to the analysis of the V/PD database, it is relatively common for machine operators to accidentally incur on the movement area. An incursion can result from the operator stopping too late, with the nose or other parts of a vehicle crossing over the hold-short line. This is not a design flaw of the vehicle, but rather a human factor causing the error. Third, risk-mitigation efforts could explore how humans interact with systems (von Bertalanffy, 1950)—for example, the relationships between a maintenance worker, ATC, and a pilot as the components of an operational system. The data analysis showed that runway incursions are frequently caused by poor communication between certain members of this system. In many cases, the communication failures are typically between the ground crew (e.g., vehicle driver or worker) and the tower. As mentioned previously, such failures can be a system tool issue where the radio is malfunctioning, but what is more common is poor human communication skills—that is, the driver and tower are either not understanding each other, or the driver has taken some action without permission from the tower. Finally, risk-mitigation efforts can focus on the relationship between humans (Barker, 1968) and the environment (McGrath, 1984). This was commonly demonstrated in the database where persons not directly affiliated with the airport entered the airside environment and, Figure 2-1. The umbrella of human factors and the subsets of human performance and human error, which help define the causal and contributing factors related to V/PDs.

12 Airside Operations Safety: Understanding the Effects of Human Factors on occasion, the movement area without permission. In one case, a person simply jumped a fence and encroached illegally onto a runway after gaining unauthorized access to the airport. In other cases, drivers proceeded through a gate that was either already open, or piggy-backed behind an airport employee who had just entered ahead of them. In addition to these types of environmental factors, how weather conditions contribute to human error and lead to runway incursions can be explored, although not many of such scenarios were found in the database analysis. 2.2 Introduction to Decision Making for Airport Managers and Operators As is further discussed in Appendix A, the analysis performed on the V/PD database using the HFACS methodology led to the classification of a significant percentage of the V/PDs as decision errors. For airport leaders to address decision errors effectively, they need to under- stand the human decision-making process. Decision making plays a role in the actions people take on and off the job every day. This section provides a definition of decision making, intro- duces the concepts of decision making, and then uses decision models to discuss how decisions are made. The discussion incorporates examples applicable to airfield operations. A good definition of decision making that relates directly to the airside environment is “the act of choosing between alternatives under conditions of uncertainty” (O’Hare, 2003). Within this uncertainty, there are only a few outcomes possible for the individual to select. First, they could apply a rule (i.e., predefined conditions with an associated response) or implement a choice (i.e., which one of several options does one select) (Orasanu and Fischer, 1997). In situations of high uncertainty, and assuming there is sufficient time, individuals should seek further cues and information to build a clearer mental model that would help them make a correct decision. In scenarios where time is not available, and decisions must be made quickly, individuals may need to create a novel solution. The act of deciding can further be complicated by the complexity, uncertainty, and time pressure of the decision, as well as the level of familiarity (expertise) of the decision maker (Wickens and Hollands, 2000). As a result, several models of decision making have been proposed. Two of these models are relatable within the context of aviation. The first is classical decision making. Classical decision making views decisions as black or white; it assumes that all options are known when the decision is to be made and that the current decision is not heavily affected by earlier decisions. An example of classical decision making within the context of this report is the preparation for a new type of commercial airliner (change of aircraft gauge) being deployed to the airport. The airport management and operators likely have adequate time to plan for the arrival of this new aircraft type. Each decision can be made in consultation with the necessary experts, and time is available for coordination and gathering all necessary specifics, such as aircraft heights, weights, wingspans, and servicing specifics. In other words, airport management must take into consideration the aircraft design group (ADG) impacts of the new aircraft and determine if any action is needed to accommodate it. This form of decision making applies best when time is available to assess all aspects of the scenario before making final decisions. Conversely, the model that is perhaps most appropriate for aviation, along with other high- consequence industries, is naturalistic decision making. Naturalistic decision making recognizes that there are rarely black-and-white responses in making decisions and it strives to understand how individuals make decisions in the real-world environment (Hammond, 1993; Klein, 1997; Lipshitz et al., 2001). It further acknowledges that all the facts may not be known when the decision needs to be made, and there is a flow between the current decision and the impact of

Human Factors Defined 13   earlier decisions on the current situation. Figure 2-2 provides a summary and comparison of these two decision models. An example of naturalistic decision making is decisions that are made in airfield operations during a winter storm. The decisions being made in this situation are occurring in real time, and there are numerous interactions of decisions that occur; earlier decisions will likely affect later ones. Determinations such as how many equipment operators to use, what equipment and chemicals to use and where to deploy them, and when to reduce aircraft operations or restrict parts of the airfield are all affected by previous decisions and further affect those that follow. The airport may be continuously adapting as the weather event goes on. The foundation of this dynamic decision making is situational awareness; the better it is, the better the decisions can be, which improves the operation’s chance for success. As individuals make repeated decisions, they tend to recognize and match patterns. This concept is known as “recognition primed decision making.” This process can help decrease the time necessary to decide and apply outcomes that have worked in the past to current situations (Bond and Cooper, 2006; Klein, 1997; Lipshitz et al., 2001; Orasanu, 2010; Vidulich et al., 2010). However, individuals must be careful because the outcomes that previously worked may not always work in the current scenario or in slightly different circumstances. For example, a different aircraft variant may require different procedures when loading and unloading cargo. The matched patterns that worked with the earlier variant may not apply to a new or updated model. This creates a subtle safety hazard that must be recognized. Therefore, these subtle differ- ences should be further investigated to ensure that proper decisions are made regarding the task being completed. There are some simple approaches that airfield managers and air- side operators can take to help improve decision making. First, make the feedback that personnel receive unambiguous. Clear feedback helps ensure that the desired message is received and understood by the receiver. Second, avoid delays in providing feedback. Feedback that is provided close to an event has a greater chance of being processed cor- rectly by the receiver. Last, standardize and adhere to the training that airside personnel receive. With standardized procedures and a commit- ment to training, individuals will have the necessary mental models and knowledge to process infor mation and apply it safely in a timely manner. Figure 2-2. Elements of classical and naturalistic decision making. Some simple approaches to improve decision making: • Make feedback less ambiguous • Avoid feedback delays • Standardize and adhere to training

14 Airside Operations Safety: Understanding the Effects of Human Factors 2.3 Communications Within the aviation domain, communications play a vital role in safe operations. Voice com- munications are the primary information transfer method between airport operations, ATC, and aircraft. The transfer of information in communication follows a basic model (as depicted in Figure 2-3). Several steps exist within this transfer and need to occur for communication to be successful. In Step 1, the sender broadcasts the message, such as verbalizing an instruction. In Step 2, that message is received by the intended recipient. The recipient analyzes the message in Step 3, and to complete the communication process in Step 4, the recipient provides feed- back to confirm understanding. Interactions between airport personnel driving on the airfield and air traffic controllers highlight the critical aspects of this communi- cation model. A typical communication interaction begins with the driver contacting the ATC tower with a request for clearance onto a surface controlled by the tower. ATC responds and broadcasts a message giving the driver clearance to enter the movement area. The driver receives this message, analyzes it, and replies to the message, repeating the driving clearance route back to ATC as part of the feed- back stage. This model highlights why it is essential for the driver to repeat the clearance back to ATC, because this feedback confirms the understanding of ATC’s message. If the driver were to respond to ATC’s driving clearance with a “Roger,” ATC would not receive enough feedback to confirm the driver’s proper understanding. A common fault in communications is the sender’s assumption that the message has been received after it was sent. However, as Figure 2-3 illustrates, other steps need to occur after the initial message broadcast. Namely, the message must be received, analyzed, and feedback provided to confirm the message’s receipt and understanding. Communication breakdowns occur when the sender incorrectly assumes that the three steps were successful immediately after broadcasting the transmission. A hypothetical example follows regarding communications between an airport operations vehicle (Ops 1) wanting to perform a taxiway inspection and the air traffic controller in the tower assigned to ground control: • Ops 1: Ground, this is Ops 1. • ATC Ground: Go ahead with your request, Ops 1. • Ops 1: Ops 1, request permission to drive onto Taxiway A, full length for inspection. Figure 2-3. A basic communication model depicting the transfer of information from a sender to a receiver. Breakdowns in communications can occur for several reasons, such as lack of focus, distractions, failure to confirm feedback, lack of consistency and standardization, and environmental distractions.

Human Factors Defined 15   • ATC Ground: Ops 1, state your current location. • Ops 1: Abeam the main-ramp windsock, Ops 1. • ATC Ground: Ops 1, proceed onto Taxiway A, hold short of Runway 14-32. • Ops 1: (Unintelligible) . . . Taxiway A, Ops 1. (Ops 1 proceeds onto Taxiway A and begins the inspection, but then crosses Runway 14-32.) • ATC Ground: Ops 1, hold short of 14-32! (Ops 1 clears Runway 14-32 and calls clear.) • Ops 1: Ops 1, clear of Runway 14-32. • ATC Ground: Ops 1, you were instructed to hold short of Runway 14-32; please call the tower supervisor and clear the field. • Ops 1: Ops 1, Roger. This simple exchange highlights several areas where communications broke down between the vehicle operator and ATC. First, the example highlights part of an unintelligible portion of the clearance read back that was not clarified by the message sender. Ops 1 did not make a full read back of the ATC instructions, and ATC Ground did not request a full read back when it was missed. ATC Ground assumed Ops 1 understood, given the number of times Ops 1 had been on the field and communicated with ATC. The driver of Ops 1, being a long-time veteran of airport operations, was distracted by the airport radio and missed the instruction to hold short. Ops 1 assumed the clearance allowed him to drive the length of the taxiway without stopping to hold short of the secondary runway, as was typically the case. Additionally, both parties could have sought further clarification instead of making assumptions related to the clearances provided and requests made. Table 2-1 highlights five examples of factors that can lead to communication breakdowns. A lack of attentional focus on the message being communicated could lead to missed messages or misinterpreted messages. For example, an airport driver trying to complete an inspection log entry while in the field may not be paying full attention to the radio communications and may miss an important message from ATC. As a result, when driving on the airport surface, maximum attention should be dedicated to communicating properly. Similarly, distractions can exist that cause breakdowns in communications. A coworker in the vehicle having a casual conversation can distract the vehicle operator from providing clear communications. It is recommended that vehicle drivers practice what is known as “sterile operations” when operating on the airport surface. Airline pilots are prohibited from a casual Communication Breakdown Antidote Lack of focus Avoid multitasking and focus on the messages being broadcast and received. Distractions Reduce “noise” not associated with the primary communications channel to process information accurately. Failure to confirm feedback The sender should never assume the broadcast message was received as intended by the recipient—make sure to confirm with feedback. Lack of consistency/standardization Use consistent communication protocols and follow standardized communication practices. Environmental distractions Background noise or disruptions can cause message decay or prevent the transmission of the message. Table 2-1. Common communication breakdown points and antidotes to prevent their occurrence. Sterile operations inside a vehicle cabin reduce the risk of distractions that can lead to break- downs in communications. Sterile operations, as practiced during critical phases of flight, limit communications to only those related to the task at hand.

16 Airside Operations Safety: Understanding the Effects of Human Factors conversation at all times when operating below 10,000 feet, including on the airport surface. Only communications related to the task at hand can be completed during these critical opera- tion times. This “sterile cockpit” or “sterile cab” procedure is an effective practice that is recom- mended for vehicle operators on the airport surface. The failure to confirm via feedback that a message was received, or a lack of consistency/ standardization, may also lead to breakdowns in the communication flow, both of which were highlighted in the example. However, in these cases it is the sender of the message who needs to assert responsibility to ensure feedback to their message is provided. For example, the receiver may have missed a verbal transmission due to one of the previously discussed breakdowns. Therefore, the onus is on the sender to confirm feedback is received, using proper consistency and standardization of phraseology. The last type of communication breakdown discussed in this report is more of a barrier to effective communication—that being interference related to environmental conditions. Several types of environmental distractors can draw attention away from completing a successful communication path. Loud noises, such as from aircraft auxiliary power units, can interrupt communication transfer, with a particularly strong impact on verbal communications. In these scenarios, operators should ensure that all proper devices are used (e.g., earplugs, noise-canceling headphones). Special care should be given while completing communications when these environmental factors are present to avoid communication breakdowns and to ensure accurate understanding. Environmental factor breakdowns can illustrate the need for the receiver to provide proper feedback to the sender to successfully complete the communications loop. 2.4 Introduction to Situational Awareness SA is a critical component of safe operations on an airport surface. It is necessary for all those operating on the airport to be committed to maintaining high levels of SA. SA can be thought of as an internalized mental model (Endsley, 2010). However, SA goes beyond just perceiving data from a person’s surroundings. SA consists of three levels, as depicted in Figure 2-4. A formal definition of SA can highlight the three aspects depicted in Figure 2-4: “the percep- tion of elements in the environment within a volume of time and space, comprehension of their meaning, and the projection of their status in the near future” (Endsley, 1988). In Level 1, individuals must correctly perceive their surroundings to start and develop strong SA. These elements could be related to lighting, signage, airfield conditions, weather, naviga- tional data, and vehicle systems. These cues send signals to the individual that must be processed for accurate perception to occur. In Level 2, the individual must take the information obtained through perception in Level 1 and create a meaningful understanding or comprehension of what those perceptions are indi- cating. For example, a vehicle operator could be seeing red guard lights flashing at a runway Figure 2-4. A depiction of the three levels of situational awareness.

Human Factors Defined 17   crossing, an example of Level 1 perception. However, it is the comprehension level where the operator must realize the red lights indicate it is unsafe to cross the runway and make the correct decision to hold short of the runway. Comprehension can be further affected by experience level. Novice and experienced operators could both perceive the red warning lights, but the experienced operator may have a more substantial comprehension of what those red lights mean (Endsley, 2010). In Level 3, the individual projects the future status or future actions (Endsley, 2010). This third level of SA occurs when operators take time to anticipate events that could happen in the future. For example, a vehicle operator driving across the ramp area sees, or perceives, indications that an aircraft is about to start taxiing and decides to stop the vehicle to allow the aircraft to pass. This anticipation of future events demonstrates the highest level of SA—projection. As with breakdowns in communications, breakdowns can occur with SA. These breakdowns can occur at any level of the SA hierarchy. Within Level 1, errors in perceptions may occur due to unavailable data, incorrect data, the omission of data, or forgetting the data (Endsley, 2010). Failures of Level 1 SA in the context of airfield vehicle operations could be due to, for example, misunderstanding signage or surface markings. Perceptions could be further reduced by omission or expectation bias, such as expecting the usual driving clearance from ATC and then not processing a different route that was provided. Within Level 2, errors in comprehension can occur due to a lack of a correct mental model from the perceived information or an incorrect diagnosis. Additionally, errors can arise in the comprehension level due to an overreliance on prior experience (Endsley, 2010). In these cases, expectations from previous experiences can prevent the comprehension of newer or differing material. Failures related to Level 2 SA in the context of airfield vehicle operations could be linked to correctly perceiving the information (thus supporting Level 1 SA) but not properly comprehending the meaning or significance. Perhaps ATC instructs a vehicle to expedite vacating a runway. While the driver heard and correctly perceived the message, the failure of accurately comprehending the need for the expeditious exiting of the runway could result in a Level 2 SA failure. Lastly, within Level 3, breakdowns can occur when individuals fail to project the data forward properly (Endsley, 2010). Humans tend to be poor at mental projection. Examples may be listening to a continuous flow of air traffic commands in the vehicle and incorrectly projecting conflicting clearances in the future. An example of maintaining good Level 3 SA occurred in Providence, Rhode Island, in 1999. In that event, an airliner took a wrong turn while taxiing in heavy fog. It inadvertently ended up back on the active runway. Since visual cues were blocked by the fog, the controller thought it was elsewhere on the airport and continued clearing other aircraft for takeoff. Listening to the exchange and perceiving the confusion in communications, an airliner awaiting takeoff refused its takeoff clearance by ATC and held short of the runway until the other airliner cleared the runway and reported on the ramp. Due to their cue processing and projection of the overall mental model, this crew was able to avoid a potential disaster. To maintain high SA levels, operators need to understand these three levels and their impacts on day-to-day operations. As with the process of preventing communication breakdowns, reducing distractions, seeking continual cues of information, dedicating attention, and confirm- ing anticipated outcomes can help operators maintain high SA levels. Additionally, good SA can help to provide the necessary information to make correct decisions. SA can be improved through design, training, and technology. Design can improve Level 1 and Level 2 SA through delivering clear cues to be processed by the user. Training can help ensure strong mental models of surroundings and prevent the development of bad habits or shortcuts that can infuse day-to- day operations. Technology and automation can also help provide clear cues, such as through moving map surface displays, and help operators maintain and project the current and future states of conditions on the airfield.