|Intelligent Active Dynamic Signage System: Bringing the Humble Emergency Exit Sign into the 21st Cen|
Intelligent Active Dynamic Signage System: Bringing the Humble Emergency Exit Sign into the 21st Century
By Edwin R. Galea, Hui Xie, and Peter Lawrence
Guiding people to safety and away from danger is why emergency exit signs exist. But many of today’s signage systems lack the ability to respond to a changing threat environment or to attract the immediate attention of the people needing assistance. These signs may be required by building standards and safety legislation, but their potential to be overlooked or to send people into harm’s way makes them inherently unreliable in many situations for which they are intended.
The passive nature of these emergency systems has contributed to the toll of avoidable deaths in fire and other emergencies. Tragedies involving the failure of legally compliant emergency signage systems to fulfil their basic purpose include the King’s Cross Underground fire (UK, 1987), the Düsseldorf Airport fire (Germany, 1996), the Rhode Island Night Club fire (US, 2003) and the Nairobi Westgate Shopping Mall terrorist attack (Africa, 2013) [1–4].
In the Rhode Island and Düsseldorf incidents, many people failed to see the legally compliant emergency exit signs and so did not utilise appropriate emergency exits or delayed using them, resulting in tragic consequences. In the King’s Cross, Düsseldorf and Nairobi incidents, the emergency exit signs could not adapt to the developing situation and so did not redirect people away from compromised emergency exit routes, again resulting in death. Even in the New York World Trade Center (US, 2001) disaster, the evacuation of many people was delayed because they could not find the stairs, despite the exits being marked by emergency signs .
These and other incidents have highlighted the crucial need for the humble emergency exit sign to upgrade for the 21st century. The need for exit signs that attract attention when they need to be conspicuous, to redirect people in an evolving emergency and to identify not just an exit route but the optimal exit route has driven the development of a new generation of advanced signage system. The Intelligent Active Dynamic Signage System (IADSS), developed as part of the European Commission’s FP7-funded GETAWAY project, attempts to meet these needs.
The GETAWAY project, which ran from November 2011 to October 2014, was undertaken to develop and demonstrate an innovative emergency signage system capable of providing real-time, optimal direction to building occupants during an emergency evacuation. The project was managed by BMT, with the Fire Safety Engineering Group (FSEG) of the University of Greenwich providing the technical leadership. Project partners included Ferrorcarrils de la Generalitat de Catalunya, which provided the Sant Cugat rail station in Barcelona (Spain) to test the system; Evaclite Ltd., which provided the Active Dynamic Signs; Hochiki Europe, which provided expertise with advanced fire detection systems; Vision Semantics, which developed people-counting algorithms for closed-circuit television (CCTV) systems; Kingfell, which provided practical input into how the system would be implemented as part of fire-engineered design and London Underground, which provided input into the operation of complex underground stations.
Research conducted by FSEG concerning way-finding behaviour during a simulated emergency evacuation demonstrated that most people have difficulty perceiving and hence utilising signage information . About 38% of people perceive the standard ‘green running man’ emergency exit sign (see Figure 1a) positioned directly in front of them. While most others may look directly at the sign, they do not actually ‘see’ it. It is suggested that most people are blind to standard emergency exit signs due to learned irrelevance , in which being continually exposed to, say, emergency exit signs without ever needing to use them trains the brain to ignore the signs. However, the research also showed that if the emergency exit sign was actually perceived by an individual, there was an almost 100% acceptance of the information, suggesting that if the signs could be made more noticeable, they could effectively direct people along the intended route.
The dilemma is how emergency exit signs can be made to stand out without making them larger, which architects and premises owners would rather avoid. To address this challenge, FSEG teamed up with UK company Evaclite  and developed the Active Dynamic Signage System (ADSS) concept. The ADSS uses flashing, running, green LEDs within the arrow of a standard emergency exit sign to draw attention to the sign (see Figure 1). The flashing LED lights enhance the affordance of the sign (improving signage detectability) without significantly changing the sign design, thereby reducing the risk of confusing occupants and also ensuring that the modified sign remains compliant with regulations.
The LEDs flash in a cycle of four steps to give the impression of a running sequence of lights, reinforcing the directional information provided by the arrow (see Figure 1). The flashing cycle is activated (hence the ‘active’ in device name) only once the alarm is sounded, ensuring that building occupants will not become too familiar with the concept and thus reducing the likelihood of learned irrelevance. Furthermore, the enhanced design has the advantage of failing safely, since if the LEDs fail to operate, the modified sign remains as a standard emergency exit sign.
The first part of the GETAWAY project was to test the ADSS concept to determine whether it could significantly improve the detection rate for emergency exit signs. This involved repeating the previous trials, with the standard emergency exit sign replaced with the ADSS. The results were encouraging: 77% of the participants detected the ADSS, with 100% of them following the guidance offered by the sign, an increase of 103% in detection rate compared with the conventional static signs. Furthermore, the trials suggested that, upon detecting the ADSS, the participants required an average of 1.8 s to decide on a route (i.e., to follow the sign) compared to 2.6 s for the standard emergency exit sign and 5.7 s for those who failed to see the sign . With the success of the first set of GETAWAY trials demonstrating the effectiveness of the ADSS concept, Evaclite has extended the concept to US-style emergency exit signs, with the key differences being the use of a flashing chevron rather than a flashing arrow and excluding the green running man (see Figure 2).
As demonstrated in recent real-world disasters, it is often the case that a normally viable escape route may no longer be considered safe due to the presence of hazards. It is important to convey this situational awareness information to the evacuating population through the signage system. Thus, rather than simply not activating the dynamic signs pointing to the compromised exit route, a means to effectively shut down the exit route is required. The negation concept must be easily incorporated within the standard emergency exit sign design within regulatory compliance. Above all else, the concept must be intuitive and easily understood by everyone.
FSEG and Evaclite developed with several possible design options that could be incorporated into the ADSS concept to negate an exit route. These competing designs were then tested though an international survey that involved 451 people from 10 countries. The survey showed that using a simple red cross across the face of the sign was the best option and understood by over 90% of the sample . To avoid confusion and enhance visual detectability, the bulk of the red cross is formed by solid-red LEDs, with only the first and last LEDs in the cross flashing (see Figure 3).
With the ADSS concept completed, the next stage of the GATEWAY project was to test the concept in a full-scale evacuation trial. Two trials were conducted at Sant Cugat station in Barcelona. The first trial used the conventional emergency exit signs to establish a baseline response, while the second trial used the ADSS. The two trials included test subjects who were unfamiliar with the station’s layout, did not involve staff intervention and utilised only a voice alarm system to indicate that an evacuation was necessary. In both trials the same alarm message was used without reference to the emergency signs.
The participants were placed at fixed locations distributed throughout the length of the platform. Four exits from the platform were located immediately behind the starting location of the participants and distributed almost uniformly along the platform length.
All four exits were available during the first trial. In the second trial, the first three exit routes were negated by the ADSS, with the only viable exit from the platform being the fourth exit at the far end of the platform. In the second trial the only viable exit was not the nearest exit for the majority of the participants and therefore required them to adopt a different behaviour from that exhibited in the first trial.
In the first trial, 99% of the participants exited the station using their nearest exit. Although this exit selection behaviour was consistent with the signage system, only a few participants were identified as actively looking at the conventional static signs. Thus it is unlikely that the conventional emergency signs actually influenced the escape route selection, with proximity to a viable exit probably being the main motivation for exit choice. This assumption was confirmed by the questionnaire results, which indicated that signage accounted for only 27% of participant exit selection, while the most significant factor, which accounted for 51%, was the proximity of the exit to the evacuating population.
In the second trial, only 54% of the population used their nearest exit (excluding those who were initially near the only viable exit). Thus a large portion of the participants followed the ADSS to use the distant viable exit. However, it was hoped that a higher proportion of participants would have used the viable exit indicated by the ADSS. The reason for the lower usage of the ADSS was suggested by the response to the questionnaires. While many of those who had used their nearest exit realised that the red flashing cross meant that they should not use that exit, they were not provided with an alternative. The flashing green arrow sign located above the fourth exit could not be seen easily by those who were located at the other end of the platform some 40 m away. It was concluded that if a route is to be negated (provide negative information), then an alternative route would also need to be indicated (provide positive information).
For the next series of trials, the ADSS was modified so that all the emergency exit routes would be indicated at each signage location (see Figure 4). Thus if one route was considered not viable, an alternative route would be indicated.
The trial was repeated with the modified ADSS (see Figure 4) and with all the trial participants located at the other end of the platform 40 m from the viable exit. Once again, the first three exits were negated, with only the fourth exit being considered viable. However, in addition to negating each non-viable exit, a flashing green arrow pointed the way to the viable exit. This trial was considered more challenging than the first two, as in this case, the population would need to walk past three exits before reaching the fourth and final, viable exit. In this trial, only 34% of the population utilised their nearest exit (the first exit), and 66% of the population chose to use the fourth exit. Clearly, providing both positive and negative information at each signage location improves the effectiveness of the ADSS.
The final part of the GETAWAY project was the introduction of ‘intelligence’ into the ADSS, which is achieved through two distinct support systems developed to work along with the ADSS (see Figure 5). The first is an information-gathering system that provided up-to-the-minute situational awareness to the IADSS. This information included the number and distribution of occupants and the presence of fire hazards such as smoke, heat and toxic gases. The population information was collected through the CCTV system monitoring the station platform and determined using a people-counting algorithm developed by GETAWAY partner Vision Semantics. The state of the fire environment was reported through a simulated fire detection system based on state-of-the-art system provided by GATEWAY partner Hochiki Europe.
The second system is an intelligent component known as the ‘Decision Engine’ (DE) used to identify the optimal exit path. The DE uses the fire signature information provided by the detection system and a pattern-matching algorithm developed by FSEG to identify which pre-determined fire from a fire library most closely matches the detected fire signature. The fire library contains an extensive range of pre-simulated fires produced using the SMARTFIRE CFD fire simulation software .
The population distribution and identified fire are then loaded into the building’s EXODUS evacuation simulation software, which proceeds to run through a list of pre-determined evacuation strategies for the structure. Using the Safe Egress Route Metric (SERM) algorithm developed by FSEG, the DE interrogates the simulation results and ranks the strategies from best to worst based on factors such as projected fatalities and injuries, distance travelled, evacuation time, number of stairs used and so forth. The algorithm also provides an estimation of uncertainty for each case. The ranked evacuation strategies are then presented to the human controller, who makes the final decision as to which is the best option to implement. The identified exit strategy is then implemented using the ADSS.
When activated, the ADSS indicates not only which way to go to reach safety, but just as important, where people should not go. In this way, the IADSS directs occupants to their optimal exits while at the same time avoiding potential non-viable routes.
The complete IADSS was demonstrated in a series of trials at Sant Cugat. The aim was to demonstrate that the system could identify the optimal evacuation route within the time between the fire detection system identifying a possible fire and alarm activation. A simulated fire was used as the test fire, which was different from all the fires in the fire library, and the response of the alarm system was also simulated. Test participants were distributed on the platform as in the previous trials, and the people-counting algorithm provided an approximation of the number and location of people on the platform. The station had seven possible evacuation strategies, and so seven possible evacuation scenarios were pre-programmed into the DE to be run using building EXODUS [5, 6].
The entire software package ran on a multi-core PC (multi-threaded quad core system). The simulated detection system identified a possible fire, went into Alert Mode and 30 seconds later went into Alarm Mode. The simulated fire was positioned in the vicinity of the main entrance (near the first exit), making the best evacuation strategy to use the fourth exit at the opposite end of the platform, which was the evacuation configuration tested in the earlier trials of the ADSS. Given the alert signal from the fire detection system, the DE identified a suitable fire from the fire library, and the seven evacuation simulations were run with the observed population distribution. The optimal evacuation route was selected and presented to the controller within 21 seconds, 9 seconds before the alarm was activated. The ADSS was configured, and most of the population moved to the appropriate exit. Only 42% exited via their nearest exit.
In an emergency evacuation, every second counts. Whatever the situation – from the outbreak of a fire to a terrorist attack – people instantly need to find the best route to safety. The GETAWAY project has demonstrated that the ADSS concept makes emergency signage more conspicuous, making it not only more likely that people will see the emergency exit sign but also reducing the time people spend in way finding. By including the concept of route negation, exit routes compromised by the emergency incident can be identified.
Finally, by including intelligence into the system, the IADSS can utilise up-to-the-minute situational awareness and advanced evacuation simulation to automatically select the optimal evacuation route for the population. So, while normal emergency signage may point the way to an exit, the IADSS is capable of adapting to an evolving emergency situation, leading people away from danger to safety.
Edwin R. Galea, Hui Xie, and Peter Lawrence are with Fire Safety Engineering Group, University of Greenwich