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M. Mulder

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239 records found

Journal article (2026) - Eline S. Bakker, Ferdinand Dijkstra, Clark Borst, Marinus M. van Paassen, Max Mulder
Air traffic growth leads to increasingly complex traffic situations near large airports. To support air traffic controllers in maintaining safety and improving efficiency, new support tools are needed. This paper presents the Inbound Traffic Support System (ITSS), a visual interface prototype developed in collaboration with the Netherlands’ Air Navigation Service Provider, LVNL. The interface visualizes constraints associated with the merging task and was tested for the South Sector of Amsterdam Airport Schiphol. By portraying potential merging solutions, it helps area controllers anticipate the impact of their decisions and supports their role in managing inbound traffic. Professional controllers provided positive feedback during the development phase while also identifying concerns such as display clutter that should be addressed. An experiment with semiprofessional controllers assessed the impact of the interface on operator performance and workload. Participants were instructed to rely on the interface rather than operational experience to ensure consistent results. Findings showed that the interface improved aircraft adherence to altitude restrictions and reduced the number of clearances needed in more complex scenarios. By revealing the solution space, the ITSS encourages earlier planning and reduces the need for late-stage interventions. Future work will include professional controller evaluations, increased simulation fidelity, and extended training. ...

Occurrence and impact

Journal article (2026) - D.M.L. Vlaskamp, Alex Pollitt, J. Blundell, A. Landman, Eric L. Groen, M.M. van Paassen, O. Stroosma, Max Mulder
Startle and surprise are known to impair pilot performance during non-normal flight conditions. In the past years research has focused on developing strategies to help pilots mitigate startle and surprise responses to unexpected situations. However, no equivalent research exists for cabin crew. This study investigates the prevalence, impact on crew performance, and emotional consequences of startle and surprise among cabin crew, as well as the way in which it is currently trained. A survey was conducted among 348 European-based cabin crew to gather data on in-flight events that provoked startle, surprise, or both. Objective measures included stress ratings, perceived impact on performance, perceived emotional control, training exposure, and lasting anxiety. Qualitative data were also collected to assess crew responses and coping mechanisms. Out of 348 respondents, 79.3% reported having experienced startle, surprise or both. High stress levels were significantly correlated with perceived performance impairments and lasting anxiety. Current startle and surprise training improved perceived preparedness but did not reduce perceived stress or anxiety. Emotional control was deemed a key protective factor. Startle and surprise can cause operationally significant impact on cabin crew performance. Training that includes simple, effective emotional regulation strategies, such as those developed for pilots, is currently lacking and may help improve both immediate performance and long-term psychological resilience in the cabin environment, as may increased peer-support access. ...
Conference paper (2026) - R. Palings, D.M. Pool, M.M. van Paassen, Max Mulder
Haptic Shared Control (HSC) systems offer a means to support human drivers in the transition to fully-automated driving. Matching HSC systems settings with drivers’ time-varying neuromuscular system (NMS) dynamics requires real-time HSC adaptations. This paper presents an experimental validation of a previously proposed method for predicting drivers’ time-varying neuromuscular admittance using an ‘average’ grip force scheduled linear parameter varying (LPV) model. The quality of LPV model predictions is compared to that of Recursive Least Squares (RLS) fits of an admittance model on the same data. Ten participants performed steering wheel manipulation tasks with steering wheel perturbations that needed to be kept within a certain displacement boundary by adapting their grip force. Time-invariant (TI) and time-varying (TV) boundary levels were used to, respectively, construct and validate the LPV model. Results show that the average relation between admittance and grip force that underlies the current LPV method varies too much between TV and TI tasks, hampering accurate admittance predictions. Compared to the quality-of-fit of 80-90% obtained with RLS on the TV data, the LPV model’s predictions are insufficiently accurate and do not exceed 55% on average. An approach that enables individual instead of average LPV models to be constructed directly from TV experiment data needs to be pursued for HSC implementations. ...
Objective: We aim to investigate how pilots’ startle and surprise responses affect information-processing performance during simulated in-flight events. Background: Startle and surprise are distinct constructs, each with their own potential effects on pilot’s performance during unexpected in-flight events. Prior research suggests that startle may impair performance through stress-induced cognitive interference, whereas surprise may do so via cognitive demands associated with sensemaking. Thus, we hypothesized that both startle and surprise would negatively affect information-processing performance on a secondary auditory cognitive task. Method: Using a motion-based hexapod simulator and a twin-propeller aircraft model, 26 pilots each performed eight single-pilot flight scenarios, which were designed to elicit varying levels of startle and surprise responses. Linear mixed-effects models were employed to analyse the relationships between self-report startle and surprise with secondary task performance, while controlling for individual differences and differences between the scenarios. Results: The results revealed that higher startle was significantly associated with reduced information-processing speed. For surprise, no significant association was found. Conclusion: The findings suggest that, within the context of the tested scenarios, startle appeared to impose a more pronounced disruptive effect on pilots’ information-processing performance than surprise. Application: The study underscores the need for tailored interventions to enhance pilots’ resilience to startle and calls for further research on ecologically valid methods to induce surprise for research and training purposes. ...
Journal article (2026) - Yoshinari Hashimoto, Ryosuke Masuda, Max Mulder, Marinus M. van Paassen
To achieve an efficient and stable operation of blast furnaces in the steel industry while retaining the proficient human operators’ skills, a human–machine interface based on an ecological interface design (EID) was developed. EID is an interface design framework that reduces the cognitive workload of human operators by providing essential information on the controlled system in an intuitive way. The developed interface allows the operators to explore the possible control actions, by presenting the future predictions of the controlled variables when hypothetical control actions are taken, using a transient model. In addition, a graphical representation of the mass and energy balance that links the manipulated variables and controlled variables is provided to raise the situation awareness of the blast furnace operation. The developed interface is beneficial to determine appropriate control actions that maintain hot metal temperature and production rate near the target values and keep pressure drop below the upper bound while reducing carbon intensity and production costs. ...

Enhancing driver preparedness through hazard awareness. A 15-year cohort study

Journal article (2026) - Jorrit Kuipers, Max Mulder, Maran Voskes
This cohort study investigates the long-term effects of simulator-based hazard awareness training (HAT) on learner and novice drivers in the Netherlands, using a dataset of 2,372 participants over a 15-year period. Most prior studies on HAT have measured only immediate post-training outcomes; no longitudinal cohort study with a control group has previously examined both supervised and unsupervised driving outcomes over a multi-year horizon. Although the HAT and control groups showed small but statistically significant differences in gender composition, education level, and fear of driving at the start of training, the effect sizes were negligible (d ≤ 0.09), and these characteristics are addressed as covariates in the analyses.HAT improved performance during simulator training and supervised driving: HAT students’ viewing skills were better during the intersection test, required fewer on-road training hours, passed the driving exam in fewer attempts, and achieved a higher first-attempt pass rate than the control group. These benefits did not persist into unsupervised post-licensing driving. Violations, errors, and accident involvement were comparable between HAT and control group drivers in the first and last year after licensing. Personal characteristics — including gender, licensing age, self-assessed driving competence, and subjective driving difficulty — were stronger and more lasting predictors of post-licensing behaviour than training type. These findings suggest that hazard awareness is a trainable skill, but that training effects on risk-taking behaviour are moderated by individual characteristics that emerge most clearly once drivers operate independently, aligning with findings of a previous study on the same dataset. Teaching higher safety margins during supervised driving may offer a more durable route to reducing accident risk for novice drivers than higher-order skill training alone. ...

From Fourier to filtering - Theory

Engineering Signal Analysis is an introductory textbook on the analysis of signals in time and frequency domain. It discusses how to characterize, model, analyze, interpret and operate on signals in time and frequency. In the first part of the book the basic theoretical concepts are introduced in continuous time, covering the Fourier Series and Fourier Transform. The second part introduces discrete-time signals, addressing sampling and finite signal duration, and their implications on spectral analysis. The third part elaborates on spectral estimation, covering the basic periodogram and more advanced methods. The fourth part concludes the book with an introduction to linear system theory, and addresses in particular signal filtering. ...
Conference paper (2026) - Y.D. Li, D.M. Pool, Max Mulder
InceptionTime neural network models were trained to detect distractions in manual control tasks with pursuit and preview displays. Training and test data were collected in an experiment where ten participants were deliberately distracted from the primary control task using the Surrogate Reference Task. Overall, distractions are easier to detect in pursuit tasks, with test accuracies of around 80% and 60% for pursuit and preview data, respectively. With preview, human controllers see the future target trajectory, which enables them to mitigate distraction effects. Unexpectedly, data with longer distractions from ‘hard’ secondary tasks are more difficult to classify than ‘easy’ distractions; an effect attributed to differences in human behavior between the training and test data collection conditions. These results show clear opportunities for neural network models to detect distractions, in real-time, for increasing safety of human-operated vehicles. ...
Conference paper (2026) - T.F. Eppenga, D.M. Pool, M.M. van Paassen, Max Mulder
A pursuit-tracking manual control model is introduced that includes an observer-like internal model to predict human detection of a change in controlled element dynamics. The internal model’s innovation signal, the difference between the observed and expected system response, is studied for its capacity to drive the detection of a change. The model’s performance is tested for different crossover frequencies, remnant power ratios, observer gains, and detection threshold settings, through Monte Carlo analysis of simulated pursuit-tracking tasks where the controlled element transitions from single to double integrator dynamics. The model shows highly accurate detection performance for a wide range in the observer gain, with a true positive rate of approximately 1 and a false positive rate of approximately 0.02. The high true and low false positive rates, combined with average detection times that match experimental human-in-the-loop data, show the observer model’s potential for accurately predicting human detection of a change in controlled element dynamics. ...
Conference paper (2026) - K.N. Huijsing, D.M. Pool, M.M. van Paassen, Max Mulder
Haptic shared control systems that support drivers by means of added torques on the steering wheel are often tuned heuristically. To allow for more systematic design, this paper focuses on the Four Design Choices Architecture (FDCA) and systematically analyzes its tuning with an offline simulation model for the driver’s control behavior and neuromuscular system. These analyses indicated that within the FDCA architecture the Level of Haptic Support (LoHS), which is a feedforward channel supporting negotiation of upcoming curves, is a main contributor to joint system performance. In a driving simulator experiment, the adaptation to and acceptance of different LoHS levels was investigated. Driver acceptance was found to increase with increasing LoHS values up to 1. Objective metrics, including torque conflict (70% reduction), steering effort (81% reduction), steering wheel reversal rate, and lateral deviation all improved, indicating that with the FDCA a high LoHS is both acceptable and, in fact, preferred. ...

Increasing Vigilance Using Fictional Aircraft

The introduction of more advanced automation in air traffic control seems inevitable. Air traffic controllers will then take the role of automation supervisors, a role which is generally unsuitable for humans. Gamification, the use of game elements in non-gaming contexts, shows promising results in mitigating the effects of boredom in highly automated domains requiring human supervision. An example is luggage screening, where dangerous items are rarely found, through projecting fictional threats on top of x-ray scans. This paper presents and experimentally tests a proposed implementation of gamification within highly automated en-route air traffic control. Fictional flights were superimposed among automatically controlled real traffic, thus creating fictional conflicts that needed resolving. System supervisors were tasked to supervise the behaviour of a fully automated conflict detection and resolution system, while manually routing fictional flights safely and efficiently through the sector, avoiding conflicts with both real and fictional flights. Automation anomalies were simulated, as well as an automation failure event, after which the system supervisor needed to assume manual control over all traffic. The presence of fictional flights increased self-reported concentration levels and reduced boredom. However, some participants reported that fictional flights were distracting. Thus, while the use of fictional flights increases engagement, it might negatively affect other cognitive functions, and with that, compromise safety. Thus, while the implementation of such a tool might provide benefits in terms of skill retention and engagement, further research is recommended involving professional air traffic controllers, improved measurement tools and a longitudinal study that better excites boredom, complacency, and skill erosion in order to understand and mitigate its negative effects. ...
Journal article (2025) - Mats Dirkzwager, Ferdinand Dijkstra, Clark Borst, Marinus M. van Paassen, Max Mulder
On final approach, an approach controller is responsible for separating aircraft lining up on the instrument landing system. In an attempt to increase traffic throughput, especially in strong headwind conditions, European regulation advises all European airports to move from distance-based to time-based separation. This effectively changes the controller’s task from a distance-based to a time-based problem. Further complications arise because of the European recategorization of aircraft types initiative, and experts fear that the gains foreseen with time-based separation will not be realized. This paper presents a visual tool integrated into the radar screen to assist controllers in performing time-based separation, the ideal turn-in point (ITIP) display. To assist controllers in selecting optimal approach strategies, starting from the moment aircraft enter the terminal control area, the display shows the possibilities and restrictions in the system rather than giving (restricting) advisories. A proof-of-concept experiment was performed with people knowledgeable in air traffic control (N = 8) and compared the ITIP to a current industry state-of-the-art display designed by U.K.’s National Air Traffic Services in scenarios of varying difficulty. Results show that with the ITIP tool, efficiency improved with similar or higher levels of safety and similar or lower workload. These promising results justify testing the interface with professional air traffic controllers. Future work aims at reducing clutter, increasing simulation fidelity, and increasing the level of support in complex traffic situations. ...
Conference paper (2025) - M. Barragan, D.M. Pool, M.M. van Paassen, Max Mulder
While human control behavior is well-understood in continuous control tasks, little is still known about how human operators detect sudden changes in the controlled element dynamics. This paper focuses on modeling this detection phase for pursuit tracking tasks. Potential triggers for the human operator to detect changes in the controlled element dynamics were investigated via a time-varying computer simulation. Based on the results, hypotheses were generated and later tested in a single-axis pursuit tracking experiment with fifteen participants. Transitions from approximate single to approximate double integrator dynamics and vice versa were investigated, for which participants indicated if they detected the transition by pressing a button. Using the button push data, a model for each transition was developed and validated. The models work under the assumption that human operators use a threshold, a multiple of the steady-state standard deviation, on certain signals to detect transitions. The models developed for the transition from single to double integrator dynamics and vice versa are proposed to trigger on the tracking error and system output acceleration, respectively. They have an accuracy of 88.9% and 99.4%, respectively. However, a consistent underestimation of the detection lag remains a limitation of both models. Nonetheless, this research helped confirm the tracking error can be used in a model for the transition from single to double integrator dynamics, proposed a model for the opposite transition, and identified that the relationship between control inputs and the system's response as a crucial factor for the detection. ...
Air traffic control is advancing digitalization by developing advanced decision-support systems, where the way information is presented to operators plays a central role in shaping performance. However, the effects of different visual representations within these systems on human decision-making remain not fully understood. In this study, we compared two Conflict Detection and Resolution (CD&R) tools: the Highly Interactive Problem Solver (HIPS) and the Solution Space Diagram (SSD). Although both systems are grounded in the same control problem, they differ in how they represent the control constraints that define conflict conditions and feasible responses. Through a human-in-the-loop experiment under low-and high-traffic conditions, we analyzed how these differences influence decision-making. Results showed that, particularly in low-density traffic, HIPS enabled quicker responses, fewer commands, and smaller safety margins, whereas SSD, despite receiving more favorable subjective ratings, led to greater variability in actions. These findings suggest that visualization significantly impacts decision-making consistency and efficiency. However, in highly complex environments, overall effectiveness may depend more on operators' ability to shift and adapt decision-making patterns facilitated by the interface than on specific visual elements. ...

Reported prevalence and application of mitigation strategies

Journal article (2025) - D.M.L. Vlaskamp, Alex Pollitt, James Blundell, H.M. Landman, Eric L. Groen, M.M. van Paassen, O. Stroosma, Max Mulder
Startle and surprise can impair pilot performance and affect flight safety. This study investigates the prevalence of different startle and surprise events among helicopter pilots, its impact on pilot stress and mental effort and the influence of training background. It also looks at currently used startle mitigation strategies and evaluates the usability of a previously proposed “Aviate, Breathe, Check (ABC)” startle management method (Piras et al. 2023). A survey among 234 helicopter pilots revealed that 96% had experienced impactful startle or surprise events during operations. Scenarios such as disorientation, tail rotor incidents, and flight into instrument meteorological conditions (IMC) were considered particularly stressful. Reported levels of stress and mental effort during startle and surprise events did not differ between pilots with higher and lower experience levels or between pilots with a different training background (military or civilian). Only 38% of pilots indicated they were specifically trained to deal with startle and surprise and only 1% were trained to use a breathing technique. Most pilots (90%) expressed openness to implementing the ABC method and expected benefits from using it. Concerns regarding time constraints in critical situations emerged as the primary objection to adopting this technique. Overall, the findings indicate that the introduction of a startle management method tailored for helicopter operations could significantly enhance safety, especially given the higher accident rates compared to fixed-wing operations. Future research should focus on developing effective training protocols that account for the unique challenges of helicopter flying. ...
The identification of time-varying, adaptive behavior of a human operator in basic manual control tasks is currently still a focus area, since most methodologies only account for time-invariant system dynamics. Previous authors have proven that estimation techniques based on ARX model structures can be used to identify time-varying HO model parameters. However, ARX methods do present several problems, such as a persistent bias in the obtained estimates of the HO model poles (neuromuscular parameters) that increases due to coupled noise and system models. Therefore, in this paper a novel identification technique based on Box-Jenkins (BJ) models is proposed, to achieve a better match between the BJ estimator's inherently uncoupled system and noise models and measured HO control dynamics. The identification process was tested offline (batch-fitting) using Ordinary Least Squares and the Prediction Error Method for both ARX and BJ models, respectively, or online when Recursive Least Squares and Recursive PEM are employed. The BJ estimator has excellent potential as an identification tool due to its bias reduction capabilities, as clearly shown in batch-fitting, although the non-linear optimization processes decrease its convergence speed by 500%. An RPEM algorithm with a forgetting factor of λ = 0.99609 and a first-order remnant model incorporated in the BJ structure was tested on Monte Carlo simulation and experimental data. While the recursive BJ estimator showed the same bias-diminishing advantages also seen in batch-fitting, the non-linear RPEM estimator's results showed much slower convergence after HO behavior adaptations and frequent instabilities of the obtained parameter estimates. Hence, further research is needed for implementing a practical bias-free HO model estimator based on the BJ model structure. ...
We tested whether pilots would detect low-salient controllability problems more quickly during manual compared to automated flight. Using a moving-base simulator and a Piper Seneca aerodynamic model, airline pilots (n = 20) performed scenarios in which either a gradually ensuing single-engine failure or an icing accumulation occurred. Both scenarios were performed once during manual flight and once during automated flight, and were alternated with distraction scenarios. The icing accumulation was detected marginally significantly more quickly during manual flight, while there was no significant difference for the engine failure. Problems in manual flight were, as expected, most likely discovered from aircraft motions or control forces. Interestingly, there were several late detections during manual flight which appeared to be caused by subconscious manual corrections. In automated flight, the engine failure was discovered most often from the engine manifold pressure indication, while the icing accumulation was most often discovered from control column movement. The results therefore underline the importance of using back-driven controls, and further indicate that manual flight does not necessarily improve detection of problems that occur without display indications. ...
An online pilot manual control behavior identification method, based on recursive low-order time-series model estimation, is presented and validated using experimental data. Eight participants performed compensatory tracking tasks with time-varying vehicle dynamics, where, at an unpredictable moment during a run, a sudden degradation in dynamics could occur. They were instructed to push a button when they detected a change in dynamics. Two methods to automatically detect the moment when pilot adaptation occurs from online estimated parameter traces are discussed. Results show that pilots are more accurate in detecting changes than either algorithm. But when the algorithms are correct, they are often quicker to detect pilot adaptation than pilots themselves. The presented techniques have potential but need improvements. ...
This manual provides guidance for human factors researchers and applied psychologists, on the standardized and scientifically rigorous use of the instruments. It is structured to include an overview of the instruments, administration guidelines, and a summary of their psychometric properties to support accurate application and interpretation in research and operational contexts. ...