Dissuasive exit signage for building fire evacuation

Applied Ergonomics 59 (2017) 84e93

Contents lists available at ScienceDirect

Applied Ergonomics journal homepage: www.elsevier.com/locate/apergo

Dissuasive exit signage for building fire evacuation Joakim Olander a, Enrico Ronchi b, *, Ruggiero Lovreglio c, Daniel Nilsson b a

Holmes Fire, New Zealand Department of Fire Safety Engineering, Lund University, Sweden c Department of Civil and Environmental Engineering, Technical University of Bari, Italy b

a r t i c l e i n f o

a b s t r a c t

Article history: Received 11 May 2016 Received in revised form 9 August 2016 Accepted 26 August 2016

This work presents the result of a questionnaire study which investigates the design of dissuasive emergency signage, i.e. signage conveying a message of not utilizing a specific exit door. The work analyses and tests a set of key features of dissuasive emergency signage using the Theory of Affordances. The variables having the largest impact on observer preference, interpretation and noticeability of the signage have been identified. Results show that features which clearly negate the exit-message of the original positive exit signage are most effective, for instance a red X-marking placed across the entirety of the exit signage conveys a clear dissuasive message. Other features of note are red flashing lights and alternation of colour. The sense of urgency conveyed by the sign is largely affected by sensory inputs such as red flashing lights or other features which cause the signs to break the tendencies of normalcy. © 2016 Elsevier Ltd. All rights reserved.

Keywords: Dissuasive Emergency signage Exit sign Paired comparison Evacuation Dynamic signage Route choice Risk perception Urgency

1. Introduction The use of exit signage is an important component in people way-finding in case of evacuation. In this context, evacuees can have a tendency to move towards familiar routes (Sime, 1985). This is associated with a possible sub-optimal use of emergency exits, i.e. people tend to go towards the entrance of the building rather than using emergency exits (Nilsson, 2009). However, evacuation experiments in buildings have yielded results which show that emergency signage can influence the behaviour of people during an evacuation and that this depends on how visible the signs are. Experimental work (Xie, 2011) showed that only 38% of people actually detect conventional static emergency signage (e.g. based on ISO standards (International Standards Organization, 2011)), even if they are provided with unobstructed vision to signage directly in front of them. The importance of emergency signage is associated with the compliance of people with it (Duarte et al., 2014; Vilar et al., 2014; Wogalter et al., 1993, 1989). Signage has also been investigated in Virtual Reality in relationship with

* Corresponding author. E-mail address: [email protected] (E. Ronchi). http://dx.doi.org/10.1016/j.apergo.2016.08.029 0003-6870/© 2016 Elsevier Ltd. All rights reserved.

environmental features (Vilar et al., 2013). A possible way to improve people awareness of the existence of emergency signage is the use of flashing lights in the immediate proximity of the emergency sign (Nilsson, 2009). This will alert occupants of the specific emergency sign and in most cases influence the occupants to use that particular path for egress making it possible to alter behaviours such as heading back down the known path. The use of for example flashing lights, or other dynamic features incorporated into emergency signage is generally called dynamic signage system. Experimental studies show that an increase from 38% to 77% in the visibility of the signage could be observed when comparing dynamic signage systems to the more conventional static emergency signage systems (Galea et al., 2014). This conclusion was obtained by replicating an experiment performed with static signs using a dynamic exit sign. The dynamic nature of the sign was obtained using a set of LED lights which activated and pointed towards the exit. In other words, a larger portion of the egressing occupants is able to detect the sign and subsequently follows the instructions provided by it. Processes that subsequently impact observers' choice to follow signage are discussed frequently within relevant literature. A common classification includes a four step assessment based on the answer to these questions: Is the sign

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

visible to the observer? Is the sign noticed by the observer? Is the sign correctly interpreted by the observer? Does action occur due to the signage impacting the observer? (Ronchi et al., 2012; Xie, 2011). The act of incorporating dynamic features into emergency signage has been researched in different research projects. Experimental studies investigated how egress route can be indicated through the use of evacuation signage provided with lit green arrows or red crosses (Bryant and Giachritsis, 2014). Another experiment found that an egress route equipped with green flashing lights was used more frequently than one without (Fridolf et al., 2013). A virtual reality study showed that the design of flashing lights impact the capability of exit signs to help people identifying the existence of an egress route as well as route choice (Ronchi and Nilsson, 2015). In addition, active dynamic emergency signage can be used to both alert occupants of existing signage and also affect their choice of egress path. These are systems capable of altering which path is shown as the preferred egress route by altering the meanings of the emergency signage (Galea et al., 2014). This can be done by altering some characteristics of the sign to display a negative or dissuasive message, with the goal of dissuading the use of a particular path, and hence leading occupants down the egress routes which are not marked as negative or dissuasive. This paper aims to research and establish which type of emergency signage is best suited to convey a negative or dissuasive message to egressing occupants informing them that a certain egress route should not be used. This is done by performing a questionnaire study in which a set of features of selected dissuasive signs have been evaluated. The questionnaire design has been based on the Theory of Affordances (Gibson, 1977; Hartson, 2003). The analysis of results has been done using both statistical tests and a mixed ordered logit approach (Greene, 2010). 2. Methods A study was carried out at Lund University (Olander, 2015) to study the characteristics of dissuasive exit signage in which participants had to evaluate dissuasive exit signage using a questionnaire. The questionnaire was designed using the Theory of Affordances (Gibson, 1977; Hartson, 2003), specifically investigating the affordances associated with different types of dissuasive exit signage. Paired comparisons were used in the questionnaire to assess the best layout for a dissuasive exit signage. This technique allows having quantitatively comparison of different layouts against each other and it provides the advantages of getting statistically robust results (Brown and Peterson, 2009; Noor, 2013). Moreover, the questionnaire included a further task, in which participants need to assess the functional affordance of several dissuasive exit signage layouts using a 5-point Likert scale. The evaluation of the impact of different features of the installations on the perceived affordance has been made using three different methods, namely 1) binomial testing of the paired comparisons, 2) analysis of the Likert scale responses and 3) a mixed ordered logit modelling approach. 2.1. The Theory of Affordances The questionnaire that was used in this study is based on the Theory of Affordances (Gibson, 1977). This theory assumes that an object is perceived in relation to what it offers or affords an individual. An affordance is, hence, what the object offers the individual in relation to his or her goal. In other words, an affordance can be used to explain how people perceive things that they sense. For example, people would not only see an emergency exit as a door with a sign on it, but that door is interpreted as a mean of reaching a safe place. A modified version of this theory has been provided by

85

Hartson (Hartson, 2003). This later version assumes that the assessment of what an object offers people can be made in relation to different affordances, namely how an object can be (1) sensed (i.e. Sensory Affordance), (2) understood (i.e. Cognitive Affordance), (3) physically used (i.e. Physical Affordance), or (4) if it fulfil its intended goal (i.e. Functional Affordance). Therefore, this extended version of the theory allows researchers investigating the effectiveness of different evacuation systems depending on the assistance they offer to see, understand, use and fulfil the goal of the systems. By systematically exploring the sensory, cognitive, physical and functional affordances provided by an evacuation system, it should be possible to identify the advantages and disadvantages of an evacuation system. Since the system under consideration is a visual system (signage), physical affordance is not taken into consideration in this instance. The theory can be used to qualitatively analyse an array of possible system designs to rule out the most appropriate system in relation to a design goal. In addition, the theory has been used to design an affordance-based questionnaire, which explores different types of affordances in relation to the examined system. 2.2. Mixed ordered logit modelling This work adopts a mixed ordered logit approach to investigate the impact of different features of dissuasive exit signage on the perceived functional affordances of this signage. Mixed ordered logit models are a useful tool to achieve this goal since they provide a quantitative statistical method to perform behavioural studies aimed at obtaining a better understanding of the factors affecting human behaviour and predicting behavioural responses (Lovreglio et al., 2015). In particular, this modelling approach provides a relevant methodology for capturing the sources of influence (independent variables) that explain the ordinal variable (dependent variable) (Greene, 2010). Let yi be an ordinal variable which can vary between 0 and m (m 2 Nþ) for the i individual (i ¼ 1, …, k). It is possible to define an unobserved (or latent) continuous variable (y*i ) defined in an utility space characterized by threshold utility points (m0,…, mm1) which is related to yi ordinal variable according to Equation (1). This latent utility has an error component (ε) which is distributed as a logistic random distribution with expected value (m) equal to zero and variance (s2) equal to p2 =3 (Greene, 2010).

y*i ¼ b$xi þ ε;

ε  LðmjsÞ; m ¼ 0; s ¼ p

yi ¼ 0 if  ∞ < y*i  m0 yi ¼ 1 if m0 < y*i  m1 / yi ¼ m if mm1 < y*i  þ∞

.pffiffiffi 3 (1)

where xi ¼ {x1,i,x2,i,…,xn,i} is the n-components vector of independent variables, b ¼ {b1,b2,…,bn} is the n-components vector of parameters (to be estimated), mi are threshold values for the m ordered classes (to be estimated). Therefore, the parameters to be estimated are n þ m  1 (one of the threshold values can be fixed as reference point, i.e. m0 ¼ 0). Fig. 1 provides a graphical representation of the model described in Equation (1). Since y*i is not a deterministic quantity, it is only possible to define the probability that the i individual selects the y ordered value.

      Pi ðyjbÞ ¼ P my1 < y*i < my ¼ L my  b$xi  L my1  b$xi ; y ¼ 0; …; m (2)

86

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

Fig. 1. Graphic representation of the ordered model described in Equation (1).

L() in Equation (2) is the logistic cumulative distribution function. The b parameters can have both fixed values and their own probability distributions. The assumption of random parameters allows estimating the mixed ordered logit model (or Random Parameters Ordered Logit model) (Greene, 2010). Considering the probabilistic approach of this modelling analysis it is possible to define a likelihood function to estimate the unknown parameters in Equations (1) and (2) (Greene, 2010; Train, 2009). Therefore it is possible an evaluation of whether and how a factor affects the ordinal dependent variable depending on the p-values and the sign of the b parameters. 3. Questionnaire study An affordance-based questionnaire study was conducted to investigate the features of dissuasive signage. This consisted in two parts, namely 1) a set of paired comparisons of signage with different features and 2) a Likert-scale type evaluation of different installation setups. 3.1. Definition of signage features The dissuasive emergency signage features were presented to test participants in a virtually simulated environment. The environment included dissuasive signs on the top of an egress door placed within the corner of a hypothetical office space. The environment was drawn using the 3D modelling software SketchUp™ (Trimble Navigation, Sunnyvale, USA), and imported into the Virtual Reality game engine Unity3D™ (Unity Technologies, San Francisco, USA) to incorporate lighting effects of the signage. The selection of the specific installation setups was based on the literature available on emergency signage designs (Arthur and Passini, 1992; Duarte et al., 2014; Galea et al., 2014; Ronchi et al., 2015, 2012; Xie, 2011). Further information on the selection of the installation setups can be found in the report associated with this paper (Olander, 2015). Additional features (e.g. auditory cues) have not been taken into consideration in this work. The variables under consideration during the experiment and the corresponding installation setups are 1) Background colour (green plus red LED Xmarkings), 2) Red flashing lights (yes or no) and 3) Sign (EXIT text

or running man pictogram). The background colours under investigation were green (including red LED X-markings) and red. Previous surveys have shown that certain colours are associated with certain meanings during egress scenarios (Nilsson et al., 2005; Troncoso et al., 2015) and are highly dependent on the context upon which it is viewed (Wickens, 2013). Green is generally associated with safety, red is generally associated with danger while orange is generally associated with warning or nothing in particular (Nilsson et al., 2005). Therefore, the colour red was further examined in this study within various exit signage options to determine if it enhances the signage's meaning. As the colour orange is most often associated with warning but also with nothing in particular, it is presumed that red offers better relation to the dissuasive message that is meant to be conveyed. This is further enforced by virtual reality experiments where only orange flashing lights were used to alert egressing people of emergency signage, which showed no dissuasive results or interpretation (Duarte et al., 2014). The impact of the green background colour combined with red LED X-markings is also investigated in this study. This combination has been studied in a previous survey (Galea et al., 2014), showing that the marking consisting of the X-marking covering the entirety of the sign produced the best results in terms of understanding that a certain egress route was not to be used. The survey also investigated the impact of red flashing lights. This feature was included since incorporating dynamic elements into conventional static emergency signage have shown potential to increase the signage's visibility (Boer and van Wijngaarden, 2004; Galea et al., 2014; Nilsson et al., 2005; Ronchi et al., 2015). Moreover, the flash rate selected was 1 Hz following the recommendations presented in a previous research investigation (Ronchi et al., 2015). The selected pictograms for the signs included the running man pictogram in line with the Swedish standard (AFS, 2008) and the EXIT text layout in line with the text requirements of the New Zealand Building Code, as found in NZBC Clause F8 (NZDBH, 2012). The selected language for the text layout was English to create a higher perceptible level of affordance due to the widespread use of the English language within Sweden (where this experiment was carried out) as well as allow people from various countries to

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

participate in the survey. 3.2. Qualitative evaluation of installation setups Considering the features previously presented, it was possible to identify 8 (i.e. 23) different installation setups. In this study, only 5 installation setups were investigated (see Table 1). These installation setups were selected performing a qualitative evaluation of their overall sensory, cognitive and functional affordance as indicated in Table 1. This evaluation considered the way individual features of the signage (e.g., type of message provided, colour coding, etc.) contributed to each individual affordance. A red sign with a red X-mark was deemed to have very poor sensory affordance, so this design has been discarded up-front given the lack of colour contrast. When dynamic features (e.g. flashing lights) are used, sensory affordance is expected to significantly increase due to breaking the tendency of normalcy bias and drawing additional attention to the signage. Sensory affordance is expected to heavily rely on the signage's ability to stand out from the environment and break the tendency of normality. The signs with no red flashing lights have therefore been discarded since they were deemed to have very low sensory affordance. The only exception was the sign in which the running man was used in conjunction with the X-mark on a green background since this was deemed to have a higher sensory affordance than the corresponding case with a red background. Detailed explanations on the choice of the five selected installations are provided in the full report associated with this paper (Olander, 2015). The selected installation setups are illustrated in Fig. 2. 3.3. Questionnaire Paired comparisons were performed to identify the impact of different installation setups. This was achieved by administering four pairs of installation setups to a set of volunteer test participants facing two screens in a lecture room. Virtually modelled signs were shown in pairs on the screens. The paired comparison tests to test the range of variables were as follow: Test 1: IS1 vs IS3. This test was performed for assessing the impact of either providing red flashing lights adjacent to the dissuasive emergency signage or not.

87

Test 2: IS3 vs. IS7. This test was performed for assessing the impact of either providing a red background or a red LED X-mark to the dissuasive emergency signage with running man pictograms. Test 3: IS3 vs. IS4. This test was performed for assessing the impact of providing a running man pictogram or EXIT text to the dissuasive emergency signage. Test 4: IS4 vs. IS8. This test was performed for assessing the impact of either providing a red background or a red LED X-mark to the dissuasive emergency signage with EXIT text. This test was also provided to prevent inconclusive outcomes if participants provide a specific set of answers to tests A, B and C. The comparisons were chosen to investigate how a specific feature has an impact on the perceived affordances. Comparisons which would have investigated the same feature have not been considered (for instance IS1 vs IS3 and IS1 vs IS4 would have investigated the same feature, i.e. the impact of red flashing light, thus only IS1 vs IS3 has been performed). For each test, the participants were asked to answer five questions, assessing the efficiency of the signage, with grounds in the Theory of Affordances. The first question related to sensory affordance. The aim of this question was to establish whether certain features provide a more noticeable sign, as to heed the signage it must first be noticed. The question was as follows: (Question 1) Which of the two signs is the easiest to notice? The second question related to sensory affordance. The aim of this question was to establish if any specific features enhance or diminish the ability to clearly distinguish the markings on the dissuasive emergency signage. The question was as follows: (Question 2) In which of the two exit signs is it easiest to distinguish the details? The third question related to cognitive affordance. The aim of this question was to establish if any specific features increase the dissuasive emergency signage's ability to convey a dissuasive message causing observers to understand that evacuation should

Table 1 Selection of the setups (ISs) based on qualitative analysis of affordances (aff.). IS

Background Colour

Red Flashing Lights

Sign

Sensory Aff.

Cognitive Aff.

Functional Aff.

Screening

1 2 3 4 5 6 7 8

Green þ X-mark Green þ X-mark Green þ X-mark Green þ X-mark Red Red Red Red

No No Yes Yes No No Yes Yes

Running Man EXIT Running Man EXIT Running Man EXIT Running Man EXIT

Medium Medium Very High Very High Low Low High High

High High Very High Very High Medium Medium Medium Medium

Positive Positive Positive Positive Positive Negative Negative Positive

Selected Discard Selected Selected Discard Discard Selected Selected

The selected installation setups are in Italic.

Fig. 2. The selected installation setups.

88

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

not occur via this specific route. The question was as follows: (Question 3) Which of the two exit signs best conveys the message of not using this exit route? The fourth question related to functional affordance and provided information about which dissuasive emergency signage design is most preferred for use by the observer. The question is as follows: (Question 4) Which of the two exit signs would you prefer be used to advise you not to use an exit route? The fifth question related to risk perception. The aim of the question was to establish if any specific features cause a greater sense of urgency or risk for the observer which would in turn cause observers to be more aware of the risk of the emergency situation. The word urgency was used instead of risk as it was expected that the meaning of the term risk may vary greatly between participants (Kinateder et al., 2014). The question is as follows: (Question 5) Which of the two exit signs would result in the greatest sense of urgency of the situation? For all the above questions, participants were given the option to choose sign A, sign B or that sign A and sign B are equivalent, with the exception of the fourth question where only the option for sign A or sign B is given. Participants were also given the option to describe which features cause them to answer as they do. In addition to these five questions, the participants were also given the option to rate the tested exit signage's functional affordance individually by answering the following Liker-scale type question: (Question 6) Please rate the signage options from 1 -5 based its ability to tell you to not use an exit door (note that multiple signs may receive same score) where 1 meant worse performance and 5 meant better performance. The questionnaire also contained background questions to establish participants' age, gender, nationality, colour blindness or any eye-sight deficiencies and whether or not they have had previous experiences with fire drills or actual evacuations. Pilot testing was done to validate the questionnaire, i.e. to determine if participants would have any issues with understanding the tests or questions asked. Comments from the pilot tests were taken and incorporated into the final testing setup. 3.4. Participants Participants were recruited by spreading the information of the questionnaire study through social media and social groups. In total, 46 participants' responses were collected. Participants consisted majorly of students with only one identifying as a worker. The age of the participants was on average 23 years old, with a minimum of 19 and a maximum of 40 years. A total of 29 participants identified as Swedish while the remaining 17 identified as people of other nationalities, with the second largest group being Germans with 6 participants. On a scale of 1e5, where 1 is low and 5 is high, the participants rated their own English skill as an average of 4.6, with a low of 3 and a high of 5. Previous fire emergency experience of the participants was largely consisting of fire drills (76%) with a few participants also having experience real scenario evacuations (30%). Several participants stated having eye-sight impairments such as near and far sightedness, however this was

in all cases corrected by glasses or contact lenses. A single participants noted colour blindness. Participants' demographics and characteristics may have an impact on the perception and understanding of the dissuasive emergency signage. On one hand, this aspect was not analysed in this work since the main objective was the investigation of the impact of different features of dissuasive exit signage on the perceived functional affordances of this signage. On the other hand, the sample size was not sufficient to investigate such an impact. Future studies are, therefore, necessary to investigate this issue. 3.5. Procedure Participants were seated in a lecture hall facing two screens. On the screens were projected images of the hypothetical emergency scenario in which dissuasive emergency signage was present. During the questionnaire study, the lighting in the room was turned off for the shown images to be clearer. Virtually modelled signs were shown in pairs on the screens and the participants were asked to answer the questions described in Section 3.3 using a questionnaire sheets. Upon completion of the questionnaire study the questionnaire sheets were collected from the participants. Participants were thanked and cinema tickets were distributed as compensation for their time. Three trials were carried out with different participants (Trial 1: 16 participants, Trial 2: 14 participants, Trial 3: 16 participants). The order of tests was randomized for the different trials. In addition, the position of the signage display on the screen (left or right) was also randomized during the trials. This was done to minimize the effects of questionnaire fatigue and possible sources of bias due to the position of the signage on the screens. For ethical purposes, participants of the questionnaire study were notified of their right to withdraw from the questionnaire study at the start of the questionnaire procedure. Upon withdrawing, their questionnaire sheet would be discarded and not used. No participants chose to withdraw from the questionnaire study. Then, contact information gathered upon recruiting participants was used only to remind participants of the time and place of the questionnaire study in the days leading up to the appointed time. This contact information was not shared and subsequently destroyed when the questionnaire study procedure was completed. 4. Results Three independent methods were used to perform a thorough investigation into the questionnaire responses. The first method consisted of binomial testing of the paired comparisons. The second method used Wilcoxon-signed rank testing techniques to evaluate the Likert scale results. The third method adopted a mixed ordered logit modelling approach. The use of three independent methods to evaluate questionnaire results is deemed to provide multiple insights into the responses provided by the test participants. 4.1. Binomial testing The results of the paired comparisons were statistically analysed using binomial testing. The null hypothesis in this case was that there is no preference for any one sign over another, in other words, that the two signs of each test are expected to be preferred equally often. Table 2 shows a summary of the binomial testing results of the questionnaire. The number of responses tested varies for questions 1, 2, 3 and 5 due to responses where no choice was made or because the cases in which signs were considered equal had been removed.

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

89

Table 2 Summary of binomial testing results, where c ¼ frequency of answer, % ¼ percentage of answer and p ¼ probability of null hypotheses. Statistical significant values are presented in bold. The number of observations varies between tests. Question 1

Test IS1 IS3 Test IS3 IS7 Test IS3 IS4 Test IS4 IS8

Question 2

Question 3

Question 4

Question 5

c

%

p

c

%

p

c

%

p

c

%

p

c

%

p

0 45

0 100

.00

14 8

64 36

.29

16 26

38 62

.16

18 28

39 61

.18

0 40

0 100

.00

9 25

26 74

.01

7 34

17 83

.00

34 9

79 21

.16

34 12

74 26

.18

6 18

25 75

.00

4 7

36 64

.55

10 20

33 67

.10

12 14

46 54

.85

22 24

48 52

.88

5 6

45 55

1.00

11 26

30 70

.02

5 37

12 88

.00

37 6

86 14

.00

37 9

80 20

.00

8 27

23 77

.00

1

2

3

4

As statistical significance is checked within a 95% confidence interval and a Bonferroni correction is applied, a p-value lower than .0125 (ai ¼ 0.0125 ¼ 0.05/n, where n is the number of tests) results in a statistically significant difference from the null hypotheses. A summary of the statistically significant differences and a description of what this implies are presented here. Test 1/Question 1: A sign with pair of flashing red lights placed adjacent to it is considered easier to notice than a similar sign not provided with flashing red lights. Test 1/Question 5: A sign with pair of flashing red lights placed adjacent to it is considered to create a greater sense of urgency than a similar sign not provided with flashing red light. Test 2/Question 1: A sign with red background and no additional markings is considered easier to notice than a sign with green background and red X-markings. Test 2/Question 2: It is considered easier to distinguish the details of a sign with red background and no additional markings, as opposed to a sign with green background and a red Xmarking. Comments from the questionnaire include that a red X-marking causes the pictogram of IS3 to become difficult to distinguish. Test 2/Question 3: A sign with green background and a red Xmarking is considered more appropriate at conveying the message of not utilizing a specific exit door as opposed to a sign with red background and no additional markings. Comments from the questionnaire include that a red sign with no additional markings is easily mistaken for a regular but oddly colored exit sign. Test 4/Question 2: It is considered easier to distinguish the details of a sign with red background and no additional markings, as opposed to a sign with green background and a red Xmarking. Comments from the questionnaire include that a red X-marking causes the text of sign IS4 to become difficult to distinguish. Test 4/Question 3: A sign with green background and red Xmarking is considered more apt at conveying the message of not utilizing a specific exit door as opposed to a sign with red background and no additional markings. Comments from the questionnaire include that a red sign with no additional markings is easily mistaken for a regular but oddly colored exit sign. Test 4/Question 4: A sign with green background and red Xmarking is preferred over a sign with red background and no additional markings to defer from exit use. Test 4/Question 5: A sign with red background and no additional markings is considered to create a greater sense of

urgency than a sign with green background and red X-markings. Comments from the questionnaire include that red is associated with danger and alarm.

4.2. Likert-scale results and analysis The questionnaire also included the option for participants to rate the installation setups individually on a Likert scale from 1 to 5, where 1 was related to worse performance and 5 was related to better performance (i.e. functional affordance). Descriptive statistics are presented in Table 3. Results were further analysed using Wilcoxon signed-rank tests (see Table 4) by using IS3 as benchmark design. The choice of IS3 as benchmark design is driven by the suggestion of its use as effective dissuasive signage in previous research (Galea et al., 2014). Applying Bonferroni corrections (ai ¼ 0.0125), statistically significant differences can be observed in two cases. IS3 is rated to perform better than IS7 and IS8. This result indicates that the signage with a green background combined with red LED Xmarkings provides higher functional affordance than a signage with red background. In addition, a marginal trend may be seen showing that IS3 also performs better than IS1 (this could not be proven statistically significant). In other words, the presence of red flashing lights improves the functional affordance of a signage. Finally, no statistically significant difference was found between IS3 and IS4. This result indicates that the type of sign has negligible impact on the functional affordance. The presence of red flashing lights and the impact of the type of sign and background colour on functional affordance were investigated estimating a mixed ordered logit model. The independent variables included in this model are the dummy variables while the dependent variable is the rank stated for the functional affordance for each installation setups (see Question 6 in Section 3.3), which identify five functional affordance classes (class 1: very low functional affordance, …, class 5: very high functional affordance). The dummy variable B is equal to 1 when the background colour is red,

Table 3 Descriptive statistics of Likert scale testing. Installation Setups

N

Mean

Standard Dev.

Min

Max

IS1 IS3 IS4 IS7 IS8

46 46 46 46 46

3.11 3.59 3.65 2.20 2.02

1.35 1.10 0.99 1.22 1.29

1 1 1 1 1

5 5 5 5 5

90

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

Table 4 Wilcoxon signed rank test results of Likert scale data and effect size (r). Comparison IS3 - IS1

IS3 - IS4

IS3 - IS7

IS3 - IS8

Negative Ranks Positive Ranks Ties Negative Ranks Positive Ranks Ties Negative Ranks Positive Ranks Ties Negative Ranks Positive Ranks Ties

N

Mean Rank

Sum of Ranks

Z

P

r

14 26 6 16 13 17 7 34 5 7 36 3

18.86 21.38

264 556

2.061a

.04

.21

14.22 15.96

227.5 207.5

0.224b

.82

.02

13.29 22.59

93 768

4.425a

.00

.46

13.14 23.72

92 854

4.665a

.00

.49

Where: Negative Ranks: IS3-ISx < 0; Positive Ranks: IS3-ISx > 0; Ties: IS3-ISx ¼ 0 with x ¼ 1,4,7,8. a Based on negative ranks. b Based on positive ranks.

the dummy variable R is equal to 1 when there are red flashing lights and the dummy variable S is equal to 1 when the sign is EXIT Text. This means that 230 observations (i.e. 5 types of setups  46 participants) can be used to estimate the mixed ordered logit model. Equation (3) illustrates the specification of the latent utility function which represents the functional affordance in relation to the background colour (B), the presence of red flashing lights (R) and the type of sign (S). The values for b, r and s re normally distributed, i.e. b  Nðmb ; s2b Þ, r  Nðmr ; s2r Þ and s  Nðms ; s2s Þ.

y* ¼ bB þ rR þ sS þ const þ ε

(3)

The model specified in Equation (3) has been calibrated using a number of 300 Halton draws to simulate random distributed parameters. Table 5 illustrates the modelling results as well as the likelihood for a model including only a constant (L0), the likelihood for the proposed model (LM). Using a likelihood ratio test to compare the proposed model with the constant model, it is possible to observe that the proposed model introduces a significant improvement in terms of fitting (p ≪ 0.05). Given the definition of the functional affordance classes, Table 5 indicates that the variables having positive parameters (i.e. means for random parameters) increase the probability to have a higher

Table 5 Estimated mixed ordered logit model. Number of Respondents: 46 Number of Observations: 230 L0 ¼ 367.801 LM ¼ 333.530 AdjR2 ¼ 0.07a Variable

Description

Coeff.

p

const

Constant Mean associated with b Mean associated with r Mean associated with s Standard deviation associated with b Standard deviation associated with r Standard deviation associated with s Threshold between Class 1 and 2 Threshold between Class 2 and 3 Threshold between Class 3 and 4 Threshold between Class 4 and 5

2.438 2.648 0.793 0.117 1.678 0.019 0.011 0.000 1.783 2.825 4.263

.00 .00 .00 .49 .00 .84 .94 Fixed param. .00 .00 .00

mb mr ms sb sr ss m0 m1 m2 m3

a The adjusted McFadden's R2 is not a measurement of fitting as the R2 of the multivariate analysis.

Fig. 3. Probability Density Function (PDF) of the b parameter in the mixed ordered logit model.

degree of the perceived functional affordance whereas a negative one reduces it. In other words, the presence of red flashing lights increases functional affordance while the use of a red background instead of a green background combined with red LED X-markings decreases functional affordance. Moreover, the use of EXIT text as sign instead of a running man pictogram has negligible impact on the functional affordance since the p-value of ms is greater than .05. Therefore, this model confirms the results inferred using the Wilcoxon signed-rank tests. Finally, the model indicates that the influence of the background colour on the functional affordance is not equal among all the respondents (sb has a p lower than .05) and it has the normal distribution illustrated in Fig. 3. The distribution illustrates that there is a percentage (i.e. grey area) of respondents for whom the use of a red background increases the functional affordance.

5. Discussion Based on the affordance-based questionnaire, this paper represents a systematic attempt to evaluate the features of dissuasive emergency signage and provide recommendations on their design. The ability of an exit sign to dissuade from using the exit should be considered in the assessment of a dissuasive emergency sign design. In addition to this, to be considered a feasible design, the dissuasive emergency signage must also be able to display a regular exit sign when required, to allow its implementation into new

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

sophisticated evacuation systems and procedural solutions. The results of the affordance-based questionnaire showed that the cognitive affordance of the dissuasive signage was of most importance as it directly influenced the functional affordance (i.e. whether you use the sign as intended or not, e.g., the results of Q3 and Q4 match) and the final preference of signage amongst participants. Therefore, features which increase the cognitive affordance of the signage should be considered a priority when designing a dissuasive emergency sign. This is in agreement with the findings of Galea et al. (2014) who found that signs with dissuasive markings which were not able to convey a sufficient enough cognitive message were misunderstood by observers (i.e. only crossing out certain areas of a sign only negated certain parts of it, such as direction or movement speed). Since the whole act of creating a dissuasive emergency signage starts with the use of a regular exit sign, the most important factor becomes making observers understand that the sign no longer conveys an EXIT HERE message, but instead is supposed to convey a DO NOT EXIT HERE message. Sufficient alteration to the sign should be provided to convey this message. Therefore, once again, the cognitive affordance of the sign is proven to be of great importance when designing a dissuasive emergency sign. However, the need to also provide a sufficient amount of sensory affordance to the dissuasive signs must not be disregarded. For dissuasive emergency signage to also be effective the signage must in some way break the tendency of normality to become visible to the passing would-be observers (Nilsson, 2009). The importance of sensory affordance plays a key role towards this goal, although it is of secondary importance if compared to cognitive affordance in the overall functional affordance scores. This confirms the findings of the experiments conducted by Frantzich (2001), relating to how people fail to notice exit signs and instead follow known paths. The sensory affordance of the signs was attempted to be increased by the use of red flashing lights placed adjacent to the signage. Results show that an installation setup with a red background instead of a green background provided an increase in sensory affordance due to being both more noticeable and easier to see details. This does not conform to the findings of Wong and Lo (2007) who found that a green and white sign was more visible than a red and white sign. It may be the result of the red LED X markings causing observers to have a more difficult time viewing the green sign, than if these LED markings would not be present. However, due to providing an unambiguous message this signage option was quickly discarded as a preferred option for use, once again enforcing the notion that cognitive affordance is of the most importance for discerning functional affordance and preference of use. Within the present work, an attempt was made to increase the cognitive affordance of the signage options in different ways: The incorporation of a red LED X-marking over the signage, the use of a red background instead of a green background and the use of red flashing lights adjacent to the signage. Comments to the questionnaire revealed that quite a few participants would have wanted the red LED X-markings to be more full, or even fully drawn lines over the signs for increased visibility and understanding. However, in an attempt to come up with a feasible solution for real dynamic signage the ‘dotted’ LED X-marking was chosen, due to the possibility to actually incorporate this into real current exit signage without reducing their primary efficiency of showing current exit routes. Providing fully drawn lines may cause the original message of the sign to be obscured even when the dynamic portion of it is not activated. Only providing a red background instead of a green background or only providing red flashing lights adjacent to the signage seem to cause observers to rethink the message of the sign but the final

91

results vary heavily. This is thought to be because signs only provided with these features have not properly negated the original EXIT HERE message and are instead providing an ambiguous message, stating either danger or warning while at the same time still stating EXIT HERE. A few participants also noted that this configuration caused them to believe that the exit sign was urging them to exit through the door faster, which is the opposite of what was intended. Another evident trend is that the use of green background (including red LED X-markings) seems to perform better than a red background in terms of functional affordance. In fact, both the binomial analysis (see tests 2 and 3) and Likert-scale result analysis (see comparisons IS3 - IS7 and IS3 e IS8 as well as the mb parameter of the mixed ordered logit) illustrate that signage with green background and red X-marking is considered more apt at conveying the message of not utilizing a specific exit door. Despite this trend, the results of the binomial analysis show that signage with red background provide a higher sensory affordance, since it is considered easier to notice and allows an easier identification of the details. Moreover, the use of a red background creates a greater sense of urgency than a sign with green background and red Xmarkings. This last result can be explained by the fact that red commonly is associated with danger and alarm (Nilsson et al., 2005). The Likert-scale result analysis suggests the use of red flashing lights to increase functional affordance. Moreover, signage with red flashing lights is considered easier to notice (i.e. higher sensory affordance) and provide a greater sense of urgency. The analysis of the signs under consideration demonstrated that there is no significant difference between the use of EXIT text and a running man pictogram as sign in terms of both functional and sensory affordance. It is important to note that the current paper has investigated only the design of visual cues. Future research should consider multi-modal warnings in line with the investigations performed in the area of human factors (Baldwin et al., 2012; Haas and van Erp, 2014). In fact, in some instances auditory cues have been proven useful in communicating urgency (Edworthy, 1994) or guiding people to safety (Fridolf et al., 2013). A discussion should be made on the impact of the sample under consideration in the present study, i.e., it was mostly made by Swedish students with a consistent experience in evacuation drills. The scope of the study was the evaluation of visual evacuation systems, thus the sample characteristics are deemed to allow a generalizability of results for able-bodied adults. Nevertheless, results are deemed to have no external validity if the population under consideration includes people with sight impairments (given the low number of people declaring this type of impairment). Similarly, since a European sample has been investigated in this sample, the use of these findings should consider the fact that colours may have different meanings in different cultures (Nilsson et al., 2005; Wickens and Hollands, 2000), i.e., the applicability of findings should be carefully reviewed in light of the cultural background/context of the population (e.g., emergency exit signs are written in red rather than green in the USA, with a potential impact of this on the answers of a population including participants from there). In addition, since the present study compared only different designs for dissuasive signage, future research should also investigate the use of those designs in contrast with signage which encourage the use of a certain evacuation route. The use of a questionnaire study as a research method permitted the obtainment of a significant amount of data (46  4 binomial comparison and 46  5 ranks) with good cost-effectiveness and ecological validity. Moreover, the selected research method allowed high experimental control and repeatability of the same scenarios

92

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93

for different participants. Nevertheless, future studies should focus on the collection of objective behavioural data in addition to the subjective preference in order to further confirm the findings of the paper. For instance, future efforts may focus on the investigation of a change in meaning of a sign (from safe to not safe) adopting an objective measures (e.g. reaction time and proportion of correct answers). Such future research study is deemed to provide useful insights into the features which facilitate the transition between usable exits to unsafe ones. Questionnaire results based on stated-preference presents a set of limitations. In fact, the ecological validity of data collected in virtual settings is lower than data from a real emergency. For instance, respondents would probably be under stress during a real evacuation scenario and this might affect their interpretation of the environment. Participants' awareness of taking part in an experiment could bias the answers. Indeed, the respondents could conform their answers to what they think should the correct answer for the researcher (Lovreglio, 2016). Nevertheless, it should be noted that the type of experiments performed present higher experimental control if compared with online surveys, where the researchers have limited possibility to make sure that the respondents follow the planned experimental procedure. From a methodological perspective, the use of the Theory of Affordances for questionnaire design has shown to be suitable for a detailed evaluation of signage design. This is in line with the usage of this framework for other types of evacuation systems (Ronchi et al., 2016, 2015). The use of a mixed ordered logit model allowed a deep investigation of the relationships between the features of an installation setup and its functional affordance. Future studies should focus on investigating affordances of different types of dissuasive emergency signage to provide a deeper understanding on the effectiveness of other installation setups as well as deepening the cultural impact and other participants' characteristics (e.g. previous fire emergency experiences) on the understanding of such installation setups. This work provides results which can be used for the design of future surveys and behavioural studies investigating the impact of dissuasive emergency signage (e.g. virtual reality experiments, online surveys). In fact, the results of this study can be used as a starting information point to develop new stated-preference survey based on Efficient Design (Lovreglio et al., 2016). The final aim of the area of research discussed in this paper is therefore design optimization through information technology (allowing comparison and prioritization among different evacuation systems). The current study represents a significant methodological contribute for the assessment of optimal signage design.

6. Conclusion Based on the results of a questionnaire study with 46 participants, it has been possible to obtaining a set of recommendations that signage designers can use during the design stage of dissuasive signage. The following main recommendations can be given: 1) Installation setups affecting cognitive affordance should be prioritized since this affordance plays a major role in the effectiveness of dissuasive signage. 2) The recommended background colour for dissuasive signage is green (with red LED X-markings), if compared to a red background. 3) The use of red flashing lights is recommended since it increases sensory affordance. 4) No significant differences have been found over the two types of message coding (the written text EXIT or a running man

pictogram) under consideration, so these two features may both be used to design dissuasive signage. References € verket. AFS, 2008. AFS 2008:13 Skyltar Och Signaler. Arbetsmiljo Arthur, P., Passini, R., 1992. Wayfinding: People, Signs, and Architecture. McGrawHill Book Co, New York. Baldwin, C.L., Spence, C., Bliss, J.P., Brill, J.C., Wogalter, M.S., Mayhorn, C.B., Ferris, T.K., 2012. Multimodal cueing: the relative benefits of the auditory, visual, and tactile channels in complex environments. Proc. Hum. Factors Ergon. Soc. Annu. Meet. 56, 1431e1435. http://dx.doi.org/10.1177/1071181312561404. Boer, L.C., van Wijngaarden, S.J., 2004. Directional Sound Evacuation from Smokefilled Tunnels. Presented at the Safe & Reliable Tunnels. Innovative European Achievements, Prague, Czech Republic. Brown, T.C., Peterson, G.L., 2009. An Enquiry into the Method of Paired Comparison: Reliability, Scaling, and Thurstone's Law of Comparative Judgment. Bryant, P., Giachritsis, G.L., 2014. The GETAWAY Project - Improving Passenger Evacuation Techniques in Railway Stations. Transport Reasearch Arena, Paris. Duarte, E., Rebelo, F., Teles, J., Wogalter, M.S., 2014. Behavioral compliance for dynamic versus static signs in an immersive virtual environment. Appl. Ergon. 45, 1367e1375. http://dx.doi.org/10.1016/j.apergo.2013.10.004. Edworthy, J., 1994. The design and implementation of non-verbal auditory warnings. Appl. Ergon. 25, 202e210. http://dx.doi.org/10.1016/0003-6870(94)900019. Frantzich, H., 2001. Experiments, occupant behaviour and response time e results from evacuation. In: Proceedings of the Second International Symposium HBIF2001. Presented at the Human Behaviour in Fire. Interscience Communications, pp. 159e165. Fridolf, K., Ronchi, E., Nilsson, D., Frantzich, H., 2013. Movement speed and exit choice in smoke-filled rail tunnels. Fire Saf. J. 59, 8e21. http://dx.doi.org/ 10.1016/j.firesaf.2013.03.007. Galea, E., Xie, H., Lawrence, P., 2014. Experimental and survey studies on the effectiveness of dynamic signage systems. Fire Saf. Sci. 11, 1129e1143. http:// dx.doi.org/10.3801/IAFSS.FSS.11-1129. Gibson, J.J., 1977. Perceiving, Acting, and Knowing: toward an Ecological Psychology. Lawrence Erlbaum Associates; distributed by the Halsted Press Division. Wiley, Hillsdale, N.J. New York. Greene, W.H., 2010. Modeling Ordered Choices: a Primer. Cambridge University Press, Cambridge, New York. Haas, E.C., van Erp, J.B.F., 2014. Multimodal warnings to enhance risk communication and safety. Saf. Sci. 61, 29e35. http://dx.doi.org/10.1016/j.ssci.2013.07.011. Hartson, H.R., 2003. Cognitive, physical, sensory, and functional affordances in interaction design. Behav. Inf. Technol. 22, 315e338. International Standards Organization, 2011. ISO 3864-1:2011 Graphical Symbols Safety Colours and Safety Signs. Kinateder, M.T., Kuligowski, E.D., Reneke, P.K., Peacock, R.D., 2014. A Review of Risk Perception in Building Fire Evacuation (No. NIST TN 1840). National Institute of Standards and Technology. Lovreglio, R., 2016. Modelling Decision-making in Fire Evacuation Using the Random Utility Theory. Politecnico di Bari, Milano e Torino, Italy. Lovreglio, R., Fonzone, A., dell’Olio, L., 2016. A mixed logit model for predicting exit choice during building evacuations. Transp. Res. Part Policy Pract. 92, 59e75. http://dx.doi.org/10.1016/j.tra.2016.06.018. Lovreglio, R., Ronchi, E., Nilsson, D., 2015. A Mixed-ordered Logit Approach to Investigate Correlations among Different Affordances in Fire Evacuation. In: Boyce, K. (Ed.), Presented at the 6th Human Behaviour in Fire Symposium 2015. Interscience, Downing College, Cambridge, UK, pp. 409e420. ISBN 978-09933933-0-3. Nilsson, D., 2009. Exit Choice in Fire Emergencies: Influencing Choice of Exit with Flashing Lights. Dept. of Fire Safety Engineering and Systems Safety, Lund University, Lund, Sweden. Nilsson, D., Frantzich, H., Saunders, W., 2005. Coloured flashing lights to mark emergency exits - experiences from evacuation experiments. Fire Saf. Sci. 8, 569e579. http://dx.doi.org/10.3801/IAFSS.FSS.8-569. Noor, F., 2013. A bayesian look at the rao-kupper model for paired comparisons. Pak. J. Stat. Oper. Res. 9, 241. http://dx.doi.org/10.18187/pjsor.v9i3.569. NZDBH, 2012. Compliance Document for New Zealand Building Code e Clause F8 e Signs. New Zealand Department of Building and Housing, Wellington, New Zealand. Olander, J., 2015. Comparative Study of Dissuasive Emergency Signage (No. 5491). LUTVDG/TVBB. Departement of Fire Safety Engineering, Lund University, Lund, Sweden. Ronchi, E., Nilsson, D., 2015. A Virtual Reality Experiment on the Design of Flashing Lights at Emergency Exit Portals for Road Tunnel Evacuations (No. 3180). Departement of Fire Safety Engineering, Lund University, Lund [Sweden]. Ronchi, E., Nilsson, D., Gwynne, S.M.V., 2012. Modelling the impact of emergency exit signs in tunnels. Fire Technol. 48, 961e988. http://dx.doi.org/10.1007/ s10694-012-0256-y. Ronchi, E., Nilsson, D., Koji c, S., Eriksson, J., Lovreglio, R., Modig, H., Walter, A.L., 2015. A virtual reality experiment on flashing lights at emergency exit portals for road tunnel evacuation. Fire Technol. http://dx.doi.org/10.1007/s10694-0150462-5.

J. Olander et al. / Applied Ergonomics 59 (2017) 84e93 Ronchi, E., Nilsson, D., Modig, H., Walter, A.L., 2016. Variable Message Signs for road tunnel emergency evacuations. Appl. Ergon. 52, 253e264. http://dx.doi.org/ 10.1016/j.apergo.2015.07.025. Sime, J.D., 1985. Movement toward the familiar: person and place affiliation in a fire entrapment setting. Environ. Behav. 17, 697e724. http://dx.doi.org/10.1177/ 0013916585176003. Train, K., 2009. Discrete Choice Methods with Simulation, second ed. Cambridge University Press, Cambridge, New York. Troncoso, J., Nilsson, D., Ronchi, E., 2015. Response to Emergency Way-finding Systems by People from Different Cultures. Presented at the Human Behaviour in Fire Symposium. Interscience Communications, Cambridge, UK. Vilar, E., Rebelo, F., Noriega, P., Duarte, E., Mayhorn, C.B., 2014. Effects of competing environmental variables and signage on route-choices in simulated everyday and emergency wayfinding situations. Ergonomics 57, 511e524. http:// dx.doi.org/10.1080/00140139.2014.895054. Vilar, E., Rebelo, F., Noriega, P., Teles, J., Mayhorn, C., 2013. The influence of

93

environmental features on route selection in an emergency situation. Appl. Ergon. 44, 618e627. http://dx.doi.org/10.1016/j.apergo.2012.12.002. Wickens, C.D., 2013. Engineering Psychology and Human Performance, fourth ed. Pearson, Boston. Wickens, C.D., Hollands, J.G., 2000. Engineering Psychology and Human Performance, third ed. Prentice Hall, Upper Saddle River, NJ. Wogalter, M.S., Allison, S., Mckenna, N., 1989. Effects of cost and social influence on warning compliance. Hum. Factors J. Hum. Factors Ergon. Soc. 31, 133e140. Wogalter, M.S., Kalsher, M.J., Racicot, B.M., 1993. Behavioral compliance with warnings: effects of voice, context, and location. Saf. Sci. 16, 637e654. http:// dx.doi.org/10.1016/0925-7535(93)90028-C. Wong, L.T., Lo, K.C., 2007. Experimental study on visibility of exit signs in buildings. Build. Environ. 42, 1836e1842. http://dx.doi.org/10.1016/j.buildenv.2006.02.011. Xie, H., 2011. Investigation into the Interaction of People with Signage Systems and its Implementation within Evacuation Models (Ph.D. thesis).