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Dieser Artikel untersucht die Ursprünge und Auswirkungen eines bahnbrechenden Evakuierungsmodells, das Anfang der 1990er Jahre entwickelt wurde und den Ansatz zur Simulation von Notausgängen in Hochhäusern revolutionierte. Das von Dr. Rita F. Fahy entwickelte Modell gehörte zu den ersten, die Netzwerkmodellierung zur Vorhersage von Austrittszeiten und zur Identifizierung von Staustellen einsetzten, was den Bereich der Brandschutztechnik erheblich voranbrachte. Der Artikel untersucht die wichtigsten Merkmale des Modells, einschließlich seines Netzwerkansatzes, der Integration mit Gefahrensimulationen und der dynamischen Routenoptimierung, die den Grundstein für moderne Werkzeuge zur Evakuierungsmodellierung gelegt haben. Außerdem werden die umfangreichen Anwendungsmöglichkeiten des Modells hervorgehoben, von frühen Fallstudien in Bürogebäuden über Analysen nach dem 11. September bis hin zu Beiträgen zu Brandschutzvorschriften. Die Einrichtung eines speziellen Repositoriums stellt die dauerhafte Zugänglichkeit des Modells sicher, unterstützt die Reproduzierbarkeit vergangener Studien und inspiriert zukünftige Forschung. Der Artikel schließt mit der Betonung der grundlegenden Rolle des Modells bei der Gestaltung zeitgenössischer Brandschutzstandards und Notfallvorsorgestrategien und macht es zu einer unverzichtbaren Lektüre für diejenigen, die sich für die Entwicklung von Evakuierungsmodellen und deren Auswirkungen auf die Gebäudesicherheit interessieren.
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Abstract
EXIT89 is a pioneering evacuation model developed for high-rise building emergencies, integrating network modeling to simulate occupant movement during crises. This short communication examines its development by Dr. Rita F. Fahy, its applications in critical case studies, and its influence on fire safety codes. The impact of EXIT89 on evacuation modeling and high-rise fire safety is considered, especially in terms of how it laid foundational groundwork for contemporary models.
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1 Introduction
The need for precise evacuation modeling in high-rise buildings has grown due to the complexities associated with geometric layout, occupant behavior, congestion, and hazards such as smoke during fires. Developed in the early 1990s by Dr. Rita F. Fahy during her tenure at the National Fire Protection Association (NFPA), EXIT89 [3] was among the first tools to leverage network modeling for simulating emergency egress. Dr. Fahy’s pioneering work significantly advanced the field by addressing critical challenges in evacuation dynamics and contributing to the broader practice of fire safety engineering. The recent passing of Dr. Fahy has brought renewed attention to her enduring contributions to the field. In recognition of her legacy and the foundational role of EXIT89 in evacuation modeling, we have established a dedicated repository to ensure EXIT89 remains accessible to the scientific and practitioner communities [3]. This initiative not only preserves the reproducibility of past studies but also supports ongoing research and practical applications in egress safety.
Dr. Fahy’s memory is honoured by revisiting EXIT89’s key features and its lasting influence on evacuation modeling and fire safety standards. Furthermore, this effort underscores the importance of maintaining access to such foundational tools, ensuring their continued impact on the future of emergency preparedness and fire safety engineering.
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2 Model Overview: Key Features of EXIT89
EXIT89 employs a network model approach that simulates individual occupant movement through a set of arcs and nodes, predicting egress times and highlighting congestion within building layouts. EXIT89, originally developed as an extension of EXITT [13], was designed to handle large populations (up to 700 individuals) with a maximum of 89 nodes per floor.
While this node limit can be adjusted by programmers, the model prioritizes computational efficiency by simplifying detailed occupant interactions, avoiding excessive calculation times. Below, we detail the model’s core capabilities:
Network model approach:EXIT89 represents buildings as interconnected networks of nodes and arcs, where individual movements are influenced by density and congestion levels. This approach makes it particularly effective for modeling large populations [10].
Integration with Hazard I: The model allows for integration with Hazard I’s smoke movement simulations, enabling analysis of occupant exposure to toxic gases during evacuations [16].
Integration with CFAST:EXIT89 supports the integration of fire data from CFAST, allowing simulations to account for the effects of fire conditions, such as smoke movement and toxic gas exposure, on evacuation scenarios [11].
Speed factor function: To enhance realism and flexibility, EXIT89 includes a speed factor function, enabling adjustments to walking speeds and alignment with observed evacuation behavior [18].
Pre-evacuation times:EXIT89 incorporates pre-evacuation times as part of its broader evacuation simulation framework, allowing them to be assigned to occupants before they begin their movement toward exits. This approach reflects more realistic scenarios in which individuals interpret alarms, make decisions, or gather belongings [18].
Predefined body sizes and modes of movement: By incorporating predefined occupant sizes (small, medium, large) and – according to Predtechenskii and Milinskii [17] – three distinct modes of movement (normal, emergency, and comfortable) along horizontal paths, openings, and stairways [11, 12].
Basic occupant behavior simulation: It simulates simple behaviors, such as selecting the shortest route or exhibiting delayed response times, which can influence overall evacuation dynamics [10].
Dynamic route optimization:EXIT89 dynamically calculates optimal escape routes by identifying exits and working backward through the network to occupant nodes. As discussed in the dissertation [19], the recalculation of blocked links is a feature of EXIT89, allowing the model to reroute occupants around obstacles when a route becomes impassable (informed by Hazard I), which significantly reduces calculation times.
Population density-based speed calculation: Walking speeds are calculated based on population density using the relationships established by Predtechenskii and Milinskii [17], making EXIT89 one of the earliest models to incorporate density-based movement.
These features make EXIT89 a versatile and pioneering tool for high-rise evacuation modeling, balancing computational efficiency with realistic occupant behaviors.
3 Case Studies and Applications
Early applications of EXIT89 included an evacuation simulation for a seven-story office building with 700 occupants, where the resulting predictions closely matched actual evacuation times under both emergency and normal conditions. The model has been used extensively to predict evacuation times and inform structural and procedural changes in high-rise buildings. Furthermore, EXIT89 has been validated against data from fire drills, controlled experiments on human movement, and comparative analyses with other evacuation models [8].
World trade center analysis:EXIT89 was instrumental in post-9/11 evacuation studies, especially in analyzing occupant behavior and egress patterns from high-rise buildings. Through this model, researchers identified factors that impacted evacuation speeds, supporting improvements in safety standards and building codes [2].
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High-rise fire safety code development: Insights gained from EXIT89 have contributed to the understanding of evacuation dynamics in high-rise buildings, informing discussions around fire safety standards such as NFPA 101 [1] and other guidelines. Studies using EXIT89 have demonstrated the importance of design features such as wider stairwells and improved emergency signage to enhance evacuation efficiency and occupant safety. Additionally, EXIT89 has been applied in evacuation studies, providing insights into occupant behaviors and movement patterns [6]. These applications underscore the model’s utility in assessing evacuation strategies and can indirectly inform considerations for stairwell dimensions and emergency signage placement to enhance evacuation efficiency.
Broader applications in various building types:EXIT89 has been applied to a diverse range of structures beyond office buildings, including residential, hospitality, and mixed-use high-rises, offering valuable insights for evacuation planning. For instance, EXIT89 was employed in a comparative egress analysis of a high-rise hotel building [9], demonstrating its effectiveness in evaluating evacuation times and occupant behaviors across various scenarios.
In addition, EXIT89 has been utilized to simulate complex infrastructures such as tunnels, with customizable travel paths, delay times, and crowding effects [18].
4 Comparative Role of EXIT89 in Evacuation Modeling Landscape
Positioned as one of the foundational models in evacuation modeling, it has played a significant role in shaping the field of evacuation modelling and analysis. The influence of EXIT89 on evacuation modeling and fire safety research is effectively illustrated by the citation network presented in Fig. 1. This dynamic citation map demonstrates the connections between EXIT89 and subsequent publications, highlighting its foundational role in the field. It also illustrates thematic linkages and key developments in evacuation modeling. The direct and indirect impacts of EXIT89 on shaping emerging trends-such as advancements in density-based movement simulations, dynamic route optimization, and integration with modern fire safety standards-are clearly traceable. The map not only underscores the historical importance of EXIT89 but also situates it within a broader research trajectory that continues to influence evacuation modeling practices today.
While robust in simulating basic movement dynamics and crowd flow, EXIT89 lacks some advanced behavioral representations (as realised in state-of-the-art simulation frameworks, e.g. as presented in [14]). EXIT89 is robust in handling basic movement dynamics but lacks some advanced behavioral representations found in newer tools.
Fig. 1
Dynamic citation map visualizing connections to 50 subsequent publications stemming from the original work introducing EXIT89 [5]. The map highlights the foundational nature of this study, its role in shaping influential research, and emerging trends in evacuation modeling. Nodes represent individual studies, while connecting lines denote citation relationships, emphasizing thematic linkages and key developments across the literature
5 Example Results: Application to a Multi-story Hotel Structure
To illustrate the kind of output EXIT89 provides and how it can be interpreted, we present exemplary simulation results from the only available input file attributed to the original developer, Dr. Rita Fahy, see data files in the repository [3]. This simulation models the evacuation of a high-rise building with features strongly suggestive of a multi-story hotel-a common use case for EXIT89 in the 1990s and early 2000s [6, 15].
5.1 Inferred Building Geometry
Although the original documentation is no longer available, analysis of the input file reveals significant details about the building structure. The building contains approximately 22 floors, a conclusion drawn from node identifiers that increase in steps of 100 (e.g., 198, 298, ..., 2298), following the convention used in EXIT89 to represent floor levels.
Each floor appears to include two stairwells, labeled SW1 and SW2, which are connected vertically from top to bottom. The floors also contain one or more hallways (HA) that link the stairwells to rooms (WP) or lobbies (LO). The building features three main exits located on the ground floor at nodes 138, 139, and 298.
5.2 Simulation Results
Fig. 2a shows a screenshot of the simulation results. The simulation models the evacuation of 110 occupants, tracking each occupant’s movement between nodes and calculating cumulative clearing times for floors, stairways, and exits. Floor clearing times were 171.33 s for Floor 1 and 148.87 s for Floor 2. Stairway clearing results showed that Stairway 99 cleared in just 9.77 s, while Stairway 98 required 148.87 s to clear completely. Regarding exit utilization, the simulation revealed that the exit at Node 138 was used by 29 people and cleared by 137 s, the exit at Node 139 accommodated 29 people and cleared by 171 s, and the exit at Node 298 handled the largest number of evacuees with 52 people, clearing by 149 s. The cumulative number of evacuated occupants over time is depicted in Fig. 2b.
Fig. 2
Simulation outputs: configuration settings (left) and evacuation progress (right)
Although EXIT89 is not a spatial simulation tool in the modern sense, the network topology and output timings enable useful evaluation of egress performance. This example demonstrates:
bottlenecks at particular exits (e.g., Node 298 handling nearly 50% of evacuees),
variability in clearing times between stairways,
the ability of EXIT89 to simulate full-building evacuations in a time-resolved manner using only text-based inputs.
This section is retained to offer future users and preservationists of legacy models a transparent view into how EXIT89 functioned and what its output can reveal, even without full architectural documentation.
6 Limitations
While EXIT89 is instrumental for modeling high-rise evacuations, it has limitations in adapting complex human behavior.
Simplified behavioral modeling:EXIT89 lacks complex behavioral modeling, focusing primarily on basic actions like moving toward the shortest exit and limited delayed responses.
Limited high-density crowd dynamics:EXIT89 calculates an average crowd speed at an aggregate level (i.e. through a macroscopic approach) rather than individual speeds, which restricts its ability to accurately model high-density crowd behaviors, such as bottlenecks, jamming, and shuffling that often occur in crowded exits or narrow corridors.
Lack of detailed individual characteristics: While EXIT89 allows for predefined body sizes and speed settings, it does not simulate detailed individual traits, which can limit its realism in diverse populations with varied physical capabilities (e.g., older or individuals with functional limitations).
Limited validation (across diverse scenarios:) While EXIT89 was primarily validated in high-rise and structured environments, it has also undergone validation in other contexts, such as fire drills and people movement experiments in department stores [9]. However, its applicability in unconventional spaces (like road tunnels or open-plan venues) may still require careful calibration and further validation to ensure accuracy.
In summary, EXIT89 is a foundational software framework for structured, high-density environments. Its primary goal is to model overall evacuation flows rather than individual behaviors. Its strengths lie in handling large populations, fast computational time, density-based speed adjustments, and hazard integration, while its limitations center around simplified behavioral modeling, limited crowd dynamics at high densities, and challenges in open or unstructured spaces. However, its contributions laid crucial groundwork for subsequent evacuation model developments.
7 Future directions and ongoing relevance
EXIT89 principles continue to influence modern fire safety modeling tools and training programs in fire safety engineering. Its pioneering network-based approach remains foundational, offering a structured framework for modeling occupant movement through nodes and arcs, which is still adopted by modern evacuation tools. This methodology has been adapted and expanded in newer models, incorporating advanced behavioral features and dynamic interaction capabilities. Despite these advancements, the core principles of EXIT89 still provide a robust and scalable method for analyzing evacuation scenarios, especially in environments with complex layouts. Its influence endures in academic research and practical applications, as seen in the development of modern (open) evacuation modeling software like Vadere [7] and JuPedSim [4].
8 Conclusion
EXIT89, developed by Dr. Rita F. Fahy, is a cornerstone in high-rise evacuation modeling. It introduced essential network modeling concepts that have since evolved but remain foundational to contemporary advancements in fire and evacuation safety. EXIT89 ’s impact on fire safety codes and high-rise evacuation strategies highlights its enduring value in emergency preparedness and response. To promote its widespread, a dedicated repository has been established to make the EXIT89 framework permanently available to the community, supporting the reproducibility of past studies and enabling its application in new case studies and research efforts [3].
Acknowledgements
The authors would like to express their sincere gratitude to Karen Boyce, Daniel Nilsson, Erica Kuligowski, Peter Thompson, and Enrico Ronchi whose insightful discussions, historical knowledge, and technical input significantly enriched this manuscript.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
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