Ergonomics
ISSN: 0014-0139 (Print) 1366-5847 (Online) Journal homepage: http://www.tandfonline.com/loi/terg20
Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels Inseok Lee & Won-Gue Hwang To cite this article: Inseok Lee & Won-Gue Hwang (2015): Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels, Ergonomics, DOI: 10.1080/00140139.2015.1047803 To link to this article: http://dx.doi.org/10.1080/00140139.2015.1047803
Accepted author version posted online: 15 May 2015. Published online: 19 Jun 2015. Submit your article to this journal
Article views: 46
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=terg20 Download by: [University of Pennsylvania]
Date: 05 November 2015, At: 15:56
Ergonomics, 2015 http://dx.doi.org/10.1080/00140139.2015.1047803
Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels Inseok Lee* and Won-Gue Hwang Department of Civil, Safety, and Environmental Engineering, Hankyong National University, 327 Jungang-ro, Anseong, Gyeonggi 456-749, South Korea
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
(Received 15 October 2014; accepted 29 April 2015) A survey was conducted to examine how personal experiences affect the interpretation of the meaning of display and control colours on electric control panels (ECPs). In Korea, the red light on ECPs represents a normal state of operation, while the green light represents a stopped state of operation; this appears to contradict the general stereotypes surrounding these colours. The survey results indicated that the participants who had experience in using ECPs interpreted the colour meaning differently from the other participant group. More than half of the experienced participants regarded the coloured displays and controls as they were designed, while most participants in the other group appeared to interpret the colours in accordance with the stereotypes. It is presumed that accidents related to human errors can occur when non-experienced people use the ECPs, which are easily accessible in many buildings. Practitioner Summary: A survey was conducted to investigate how personal experiences affect the interpretation of the function meanings of coloured lights on electrical control panels. It was found that the interpretation varies according to personal experiences, which can induce accidents related to human errors while operating electrical equipment. Keywords: stereotype of colour; colour display and control; push-button switch; electric control panels; personal experience
1.
Introduction
An electrical control panel (ECP) is installed in most electrical equipment or systems as a human-machine interface to allow operators to monitor the status of the systems and control the electricity supply to the systems. These systems include factory production lines, fire-fighting equipment, air-conditioning equipment, elevators, water-heating boiler systems and others. The ECP usually comprises several controls such as push-button switches, rotary switches or emergency switches, and pictorial displays representing the status of electrical equipment. An operator usually uses the ECP to monitor and control the systems. If the operator misunderstands the systems’ status or makes an error in controlling the equipment, it can result in an accident with injuries or economic loss. According to Korea’s electrical accident statistics, human error while using ECPs was cited as one of the main causes of electrical shock accidents (KEPCO 2009). An electrical shock accident can be so severe that it results in fatal injuries, though the occurrence rate is relatively low compared to other electrical accidents. It is necessary to decrease the probability of human error while using ECPs in order to reduce the loss from electrical shock accidents. Colour-lighted push-button switches are widely installed on ECPs. A colour light installed in the switch turns on when the switch is pushed, while the system simultaneously begins to operate or stop according to the switch function, such as ‘On’ or ‘Off’ (Figure 1). The switch is a mixed-up device to be used as both a control and a display. In the ECPs generally used in Korea, the red switch is used for ‘On’ or ‘Operating’ functions, the green switch for ‘Off’ or ‘Stop’ and the yellow switch for ‘Malfunction’ or ‘Reset’. This seems to conflict with colour stereotypes and the ergonomic recommendations for the use of colours. For the design of general purpose controls, the use of red is recommended to indicate ‘stop’, ‘danger’ or ‘off; green is used to indicate ‘go’, ‘safe’, or ‘on’ and yellow is used to indicate ‘caution’ or ‘marginal situation’ (Chengalur, Rodgers, and Bernard 2004; Konz and Johnson 2004; Wickens and Hollands 2000). In the design of display lights, red is recommended to indicate ‘malfunction’ or ‘emergency’; green to indicate ‘go’, ‘in tolerance’, ‘acceptable’ or ‘ready’ and yellow to indicate ‘delay’, ‘check’ or ‘caution’ (Kroemer, Kroemer, and Kroemer-Elbert 1994; Woodson, Tillman, and Tillman 1992). Many studies also showed that the colour red is positively associated with the meaning of danger and the colour green is positively associated with the meaning of safety (Chapanis 1994; Griffith and Leonard 1997; Leonard 1999; Chan and Courtney 2001; Borade, Bansod, and Gandhewar 2008; Chan and Ng 2009; Pravossoudovitch et al. 2014). According to Chan and Courtney
*Corresponding author. Email: [email protected] q 2015 Taylor & Francis
2
I. Lee and W.-G. Hwang
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Figure 1.
Colour-lighted push-button switches used on ECPs, which are red, green and yellow, respectively, from left to right.
(2001) who surveyed the associated meanings for various colours with Hong Kong Chinese participants, the colour red is mostly associated with ‘Stop’, ‘Caution’ and ‘Danger’ and the colour green is mostly associated with ‘Go’, ‘Safe’ and ‘On’. In Korea, there are guidelines and standards related to the use of colours in machinery controls and displays: the ‘KOSHA Guide E-94-2011: Technical safety guideline for electrical devices of industrial machineries’ and ‘KS C IEC 60241-1: Safety of machinery – Electrical equipment of machines – Part 1: General requirements’ (KOSHA 2011; KATS 2012). In these guidelines and standards, seven different colours are defined and recommended for switches used in electrical devices and five different colours are recommended for display lights (Tables 1 and 2). The recommendations for the colour meanings are similar to each other in that red is used for emergent situations, green for safe or normal situations and yellow for malfunctions. Meanwhile, in the Korean law of occupational safety and health, there is a regulation for the use of colours for safety and health codes or symbols (Information Centre of the Korean Law 2015). According to the regulation, red should be used for prohibition or warning symbols, yellow for caution, blue for instruction and green for guide. This regulation, however, is limited to the colours used for safety and health codes or symbols. Therefore, it cannot be directly applied to the colours of switches and displays on ECPs. As described, the red push-button switch on an ECP is used for operating the system, with the red light kept turning on while the system is operating. The green light is for stopping the system, with the green light kept turning on when the system is stopped. It is presumed that the red colour is used to indicate that while the system is operating, the electric current is flowing and there is a risk of electrical shock. The red light appears to be designated to remind the user of the electrical shock danger. On the other hand, the green light appears to be used to indicate a safe state, i.e. free from the electric shock, because the system is not operating and therefore, no electricity is flowing in the system. However, it is questionable as to whether individuals who are not accustomed to electrical equipment and are unfamiliar with the meaning of electrical hazard would interpret the meaning of the colours as they are designed. They might interpret the meaning of the colours in a more general way according to the stereotypes, which might result in an accident due to improper operation of electrical equipment. Although ECPs are devices meant to be used by specialised operators, there are many ECPs in modern buildings which are open to the public and generally accessible. Therefore, it is necessary to study how the colour codes in ECPs can be improperly interpreted and how this can be related to the possible occurrence of human errors. Colour is widely used as a communication mode in displays and controls because it is relatively easy and quickly recognised. However, caution should be used in assigning specific colours as codes with specific meanings as it is known that approximately 4 –8% of population has difficulty in perceiving some colours (Konz and Johnson 2004) and there are
Table 1.
Meanings of colours for push-button switches (KOSHA 2011).
Colour Meaning
Explanation
Examples
Red
Operating when a dangerous or emergent situation occurs Operating when malfunction or abnormal situation occurs
Stop switch for emergency
Emergency
Yellow Malfunction Green Blue White Grey Black
Safety Forceful action No specific meaning No specific meaning No specific meaning
Display for returning to normal states Display for re-operating stopped automatic functions Operating during normal state Possible to be used in a Start or On switch Operating when forcefully activating functions Switch for returning to normal states General functions of activation except emergent stops Activation (preferred) or Stop switch General functions of activation except emergent stops Activation or Stop switch General functions of activation except emergent stops Activation or Stop (preferred) switch
Ergonomics
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Table 2.
3
Meanings of colours for display lights (KOSHA 2011).
Colour
Meaning
Explanation
Examples
Red
Emergency
Dangerous or emergent situations
Yellow
Malfunction
Malfunction or abnormal states
Green
Safety
Normal state
Blue
Forceful action
White
Neutral
Response or the state of the operator’s operation Others
When measures such as pressure, temperature, etc. exceed the limit When measures such as pressure, temperature, etc. are out of the normal range When measures such as pressure, temperature, etc. are within the normal range Pointing to a predetermined value General information
some cultural or national differences in the stereotype of colours (Chan and Courtney 2001). In addition, when using colours as a tool to inform users of meanings, the colours should be considered to enhance the conceptual compatibility in order to decrease the probability of human error and increase the system’s usability. The use of colour with other types of display like symbols or labels can affect the perceptions of the designated meanings (Braun, Kline, and Silver 1995; Braun and Silver 1995; Leonard 1999; Mayhorn et al. 2004). The current colour codes used in ECPs appear to conflict with the colour stereotype. It would be useful to understand how the personal experiences affect the interpretation of the colour-lighted switches on ECPs in an effort to decrease human error when using electrical equipment and prevent electrical shock accidents. In this study, a survey was conducted to examine how personal experiences correlate with the interpretation of the meaning of colours used in electrical devices, pictorial displays and push-button switches.
2. Method 2.1 Participants and survey methods In this study, 350 participants (318 males and 32 females) were surveyed to examine the interpretation of the meaning of the colours used in the controls and displays of electrical equipment. The pool of randomly selected participants comprised employees from several different companies, including some related to electrical equipment operation, and university students primarily from the faculty of engineering. The participants were interviewed and informed of the survey’s purpose by the researcher before they responded to the questionnaire. It took participants less than thirty minutes to complete the questionnaire. The questionnaire included the following topics: . General information: major or occupation . Experience in using ECPs and push-button switches . Proper meaning of the coloured button switches used in electrical equipment. Seven colours were presented: red, green, yellow, blue, white, grey and black. The participants were asked to select the most appropriate meaning for each coloured button switch from the following: ‘emergency (including dangerous state or emergent operation)’, ‘abnormal state’, ‘normal state (including normal operation)’, ‘necessity of forceful operation’, ‘no specific meaning’ and ‘unknown’. . Interpretation of the coloured pictorial display representing a pumping process. Two pictorial displays representing pumping processes were presented in red and green respectively (Figure 2). The participants were asked to select whether each picture represented an ‘operating state’ or ‘stopped state’.
Figure 2. A pictorial display representing the process state used in the questionnaire (The circular part around character ‘A’ was coloured as red or green).
4
I. Lee and W.-G. Hwang . Interpretation of the colour-lighted push-button switches. Three push-button switches in red, green and yellow respectively were presented. The participants were asked to select the function meaning for each switch from the choices of ‘operating’, ‘stop’, ‘abnormal/reset’.
2.2
Analysis
The participants were classified into two groups according to their majors, occupations and experience in using ECPs. Chisquare tests with a significance level of 0.05 were used to analyse the correlations between the participants’ characteristics and their responses to the questions on the electrical device switch colour meanings, the pictorial displays colour meanings and the push-button switch colour meanings. SAS (ver. 9.2) was used in the statistical analyses.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
3. Results 3.1 General characteristics of participants The participants’ ages were balanced across the following ranges: 20s (40.6%), 30s (32.0%) and 40s (23.4%). With regard to their occupations, 57.4% of the participants were employees, while 31.4% were university students and 11.1% were selfemployed or owners of small businesses. Ninety-eight participants (28.0%) studied in fields related to electrical engineering in high school or university, while the remainder studied in other fields. Most participants studied engineering or natural sciences, only 8.0% of the participants studied humanities, literature or social sciences (Table 3). One hundred and forty-four participants (41.1%) worked in occupations related to the operation of electrical equipment or machineries, while the remainder of the participants worked in unrelated fields or were students. 3.2 Experience with ECPs and push-button switches Approximately half of the participants (49.4%) answered that they had experience in using ECPs (Table 3). The ratio of the experience was found to be statistically correlated to the participants’ majors and occupations ( p , 0.05). The electrical engineering participants indicated a higher experience rate than participants not in electrical engineering (76.5% vs. 38.9%). The participants who were in occupations related to the electrical equipment or machineries also indicated a higher experience rate than the others (89.6% vs. 21.4%). 3.3
Interpretation of colours used for electrical equipment switches
The participants were asked to select the most appropriate meaning of each colour used for electrical equipment or machinery switches. The responses indicated that 77.4% of the participants selected emergent situation for red and normal state for green, and 71.4% selected abnormal situation for yellow (Table 4). For white, grey and black, most participants responded that they thought there was no specific proper meaning or that they were unaware the proper meanings (86.3 –95.1%). For blue, while more than half of the participants selected no-specific meaning or that the proper meaning was unknown (59.7%), a substantial number of participants selected mandatory operation or forceful operation (29.7%). The participants’ selections for the most appropriate meaning for the red, green, yellow and blue switches were found to be significantly correlated to their majors, occupations and experiences in using ECPs, respectively ( p , 0.05) (Tables 5). Among the electrical engineering participants, 64.3% selected emergent situation and 23.5% selected normal situation as the most appropriate meaning for the red switch, while 82.5% of the remaining participants selected emergent situation as Table 3.
Number (percentage) of participants categorised by their majors and occupations vs. experience in using ECPs (People, %). Use of ECP
Major
Electric Eng. Non-Electric Equip. Others
Occupation Total
Exp
No Exp
75 (76.5) 98 (38.9) 129 (89.6) 44 (21.4) 173 (49.4)
23 (23.5) 154 (61.1) 15 (10.4) 162 (78.6) 177 (50.6)
Total 98 (28.0) 252 (72.0) 144 (41.1) 206 (58.9) 350 (100.0)
(100.0) (100.0) (100.0) (100.0) (100.0)
Ergonomics
5
Table 4. Percentage of participants selecting the most appropriate meaning of the colours for switches on electrical equipment or machineries (%). Meanings Emergency situation Abnormal situation Normal situation Forceful operation Not specified / unknown Total
Red
Green
Yellow
Blue
White
grey
Black
77.4 1.4 12.9 0.9 7.4 100.0
0.3 1.4 77.4 2.6 18.3 100.0
6.6 71.4 0.9 4.0 17.1 100.0
0.0 1.7 9.4 29.1 59.7 100.0
0.6 2.6 0.6 10.0 86.3 100.0
0.3 2.6 0.0 2.6 94.6 100.0
0.0 1.7 0.3 2.9 95.1 100.0
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Note: The highest percentage for each colour is noted as bold.
the most appropriate meaning for red. For the green switch, the ratios of participants who selected normal situation were 69.4% of those with electrical engineering backgrounds and 80.6% of the remaining participants. Approximately a quarter of the electrical engineering participants answered that that there was no specific meaning or they did not know the meaning of the green switch. For yellow switch, the difference in meaning interpretation between the electrical engineering participants and the remaining participants was not as large as the differences in the green or red switches. For blue, the percentage of participants who selected mandatory or forceful operation was higher for the non-electrical engineering group than for the electrical engineering group (32.5% vs. 20.4%). The participants whose occupations were not related to electrical equipment operation or maintenance mostly regarded the red switch as proper for an emergent situation (82.5%), while the ratio decreased to 64.3% with the participants whose occupations are related to electrical equipment. For green switch, similar percentage results were shown for the normal situation. It is interesting to note that 26.5% of the participants whose occupations are related to electrical equipment answered that there is no specific meaning or the meaning was unknown. The most participants without experience in using ECPs believed that the red switch was proper for an emergent situation (90.4%), while of the experienced participants 64.2% indicated it was for emergent situations and 23.7% indicated it was for normal situations. The results for the green switch indicated a similar percentage pattern, with 23.6% of the experienced participants answering that there was no specific meaning or the meaning was unknown. Table 5.
Percentage of participants selecting the most appropriate meaning of the colours for displays and controls on ECPs (%).
Characteristic
Colour
Majors
Red Green Yellow Blue
Occupations
Red Green Yellow Blue
Experience
Red Green Yellow Blue
Group
Emergency situation
Abnormal situation
Normal situation
Forceful operation
Not Specified/Not knowing
Total
Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric
64.3 82.5 0.0 0.4 11.2 4.8 0.0 0.0
0.0 2.0 3.1 0.8 67.3 73.0 1.0 2.0
23.5 8.7 69.4 80.6 0.0 1.2 5.1 11.1
2.0 0.4 1.0 3.2 1.0 5.2 20.4 32.5
10.2 6.3 26.5 15.1 20.4 15.9 73.5 54.4
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Equip. Others Equip. Others Equip. Others Equip. Others
59.7 89.8 0.7 0.0 13.2 1.9 0.0 0.0
2.1 1.0 2.8 0.5 67.4 74.3 2.1 1.5
27.8 2.4 64.6 86.4 0.0 1.5 5.6 12.1
2.1 0.0 2.1 2.9 2.8 4.9 18.1 36.9
8.3 6.8 29.9 10.2 16.7 17.5 74.3 49.5
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp. Exp. No Exp. Exp. No Exp.
64.2 90.4 0.6 0.0 11.6 1.7 0.0 0.0
2.3 0.6 2.3 0.6 68.8 74.0 2.9 0.6
23.7 2.3 68.2 86.4 0.0 1.7 7.5 11.3
1.7 0.0 2.3 2.8 2.9 5.1 22.0 36.2
8.1 6.8 26.6 10.2 16.8 17.5 67.6 52.0
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Note: The highest percentage in each row is noted as bold.
6
I. Lee and W.-G. Hwang
Table 6.
Percentage of participants selecting the proper meaning of the coloured pictorial displays of a pumping process (%).
Characteristic
Colour
Majors
Red Green
Jobs
Red Green
Experiences
Red Green
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Total
Group
Operating state (ON)
Stopped state (OFF)
Total
Electric Eng. Non-electric Electric Eng. Non-electric
52.6 30.9 48.5 70.4
47.4 69.1 51.5 29.6
100.0 100.0 100.0 100.0
Equip. Others Equip. Others
61.4 20.0 38.6 82.0
38.6 80 61.4 18.0
100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp.
54.1 20.0 45.9 82.4 37.1 64.1
45.9 80.0 54.1 17.6 62.9 35.9
100.0 100.0 100.0 100.0 100.0 100.0
Red Green
Note: The highest percentage in each row is noted as bold.
3.4 Interpretation of colours for a pictorial symbol of a process In the selection of the proper meanings for the red and green pictorials representing a pumping process, 62.9% of the participants interpreted the red picture to represent a stopped process and 64.1% interpreted the green picture represent an operating process (Table 6). The participants’ interpretations of the red and green pictorial meanings were found to be significantly correlated to their majors, occupations and experiences in using ECPs ( p , 0.05) (Table 6). Among the participants whose majors are related to electrical engineering, 52.6% of the participants interpreted the red picture to indicate an operating process and 51.5% interpreted the green picture to indicate a shutdown process. In the other group, however, 69.1% of the participants interpreted the green picture to indicate an operating process and 70.4% interpreted the red picture to indicate a shutdown process. Based on occupations, the red picture was interpreted as an operating process by 61.4% of the participants in an occupation related to electrical equipment operation or maintenance, while 80.0% of the other participant group interpreted it to indicate a shutdown process. The results for the green picture were inversely similar to the results for the red picture. Similar differences in results between the experienced and inexperienced participants were attained for the interpretation of the coloured pictorials. Most inexperienced participants regarded the red picture to indicate a stopped operation (80.0%), while 54.1% of the experienced participants regarded it as being in an operating state. Interpretations of the green picture were inversed from the results of the red picture. 3.5
Interpretation of colours for push-button switches on ECPs
With regard to the proper meanings for the red, green and yellow-lighted push-button switches generally used on ECPs, 60.3% of the participants thought the red light was to stop the equipment, 67.1% selected the green light was to operate the equipment and 93.2% thought the yellow light indicated an abnormal equipment state or to be reset (Table 7). It was found that the participants’ selection of the colours’ functions or meanings was significantly correlated to their majors, occupations and experiences in using ECPs ( p , 0.05). According to the participants’ majors, 52.1% of the electrical engineering participants indicated the red light was to operate the equipment and the green light was to stop it, while 65.6% of the other group indicated that the red lighted was to stop the equipment and 74.6% indicated the green light was to operate it. The majority of participants from both groups regarded the yellow light to indicate abnormal equipment situations or the need to reset. The majority of participants in occupations unrelated to the operation or maintenance of electrical equipment regarded the red switch for stopping equipment (76.8%), while 61.3% of the participants in occupations related to electrical equipment operation or maintenance indicated it was for operating equipment. For the green switch, the results were reversed with 59.9% of the participants in occupations related to electrical equipment regarding it as a stopping function and 86.4% of the other group regarding it as an operating function. It was found that experience with using ECPs had the most differentiated effect on the selection of the coloured switch functions. For the red switch, 76.3% of the non-experienced participants selected stopping equipment and 52.6% of the experienced participants selected operating equipment. For the green switch, 85.8% of the non-experienced participants selected operating equipment and 51.5% of the experienced participants selected stopping equipment.
Ergonomics Table 7.
Percentage of participants selecting the most appropriate meaning of the colours for push-button switches (%).
Characteristic
Colour
Majors
Red Green Yellow
Occupations
Red Green Yellow
Experience
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
7
Red Green Yellow
Total
Group
Operate
Stop
Abnormal/Reset
Total
Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric
52.1 26.2 47.9 74.6 0.0 0.4
46.9 65.6 52.1 24.6 1.0 8.6
1.0 8.2 0.0 0.8 99 91
100.0 100.0 100.0 100.0 100.0 100.0
Equip. Others Equip. Others Equip. Others
61.3 13.6 40.1 86.4 0.0 0.5
37.3 76.8 59.9 12.6 1.4 10.1
1.4 9.6 0.0 1.0 98.6 89.4
100.0 100.0 100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp. Exp. No Exp.
52.6 14.2 48.5 85.8 0.6 0.0 33.5 67.1 0.3
44.4 76.3 51.5 13.0 2.9 10.1 60.3 32.4 6.5
2.9 9.5 0.0 1.2 96.5 89.9 6.2 0.6 93.2
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Red Green Yellow
Note: The highest percentage in each row is noted as bold.
4.
Discussion
In this study, a survey was conducted to examine the relationship between personal experiences and the understanding of the meaning of switch colours used in electrical equipment. The three main subjects of the questionnaire were (1) how the participants understood the meanings of the switch colours, (2) how the participants interpreted the two different coloured pictorial displays representing a pumping process, (3) and how the participants interpreted the three main colours of the push-button switches widely used on ECPs in Korea. The participants were grouped by their personal experiences including major in school, relation of occupation to the operation of electrical equipment and experiences in using ECPs. The groups were compared in terms of their responses to the questions. 4.1
Interpretation of the meaning of colours for the controls and displays
The participants were asked to select the most appropriate meanings for the seven colours recommended for electrical equipment controls in Korean safety guides or standards (KOSHA 2011; KATS 2012): red, green, yellow, blue, white, grey and black. The majority of participants answered that red was proper for representing emergency or danger, green represented a normal state and yellow represented an abnormal state (71.4 –77.4%). For white, grey and black, most participants answered that there was no specific proper meaning for those colours or they were unaware of their proper meanings (86.3 –95.1%). These results coincided with recommendations in the KOSHA Guide E-94-2011 and KS C IEC 60204-1:2012 as shown in Table 1 and ergonomics literatures (Chengalur, Rodgers, and Bernard 2004; Konz and Johnson 2004; Wickens and Hollands 2000). The only exception was the interpretation of the meaning of blue. The blue switch is recommended as a forceful operation function, which was supported by only 29.1% of the participants, while 59.7% of the participants selected ‘no specific meaning’ or ‘unknown meaning’. Based on this result, one should be cautious when employing a blue switch to indicate a forceful operation or resetting function on machinery or electrical equipment. The participants’ interpretations of the red and green pictorial displays representing a pumping process were found to be more diverse than the selection of the most appropriate meaning of the seven different colours. Though more than half of the participants regarded the red picture as representing a stopped process and the green picture as representing an operating process (62.9% and 64.1%), it is interesting to note that a substantial number of respondents inversely interpreted the two coloured displays, i.e. 37.1% regarded the red pictorial as representing an operating process and 35.9% thought the green pictorial as representing a stopped process. The participants’ results were also similar for the interpretation of the meaning of the colour-lighted push-button switches; 60.3% of the participants believed that the red light was for turning off the equipment and 67.1% believed the green light was for operating the equipment, while the others interpreted the colours differently. This diverse interpretation of colours indicates that in order to inform the users of the meanings of colours used
8
I. Lee and W.-G. Hwang
for displays and controls, additional methods such as labels or legends should be applied in order to prevent human error related to misunderstanding the colours’ purposes.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
4.2
Personal experiences and interpretation of the meaning of colours for the controls and displays
The participants were grouped into two groups according to three different criteria: whether or not their major was related to electric engineering; whether or not their occupation was related to electrical equipment operation and whether or not the participant had the experience in using ECPs. The criteria were determined to be correlated. As shown in Table 3, the experienced participants tended to have studied electrical engineering and tended be in an occupation related to the electrical equipment operation. Therefore, the relationships between these personal experiences and the interpretation of the colours revealed similar patterns, though there are some differences in the percentages (Tables 5 –7). In the selection of the proper meaning of the colours for the controls of electric equipment, the percentages of inexperienced participants who selected danger/emergency for red and normal state for green were 90.4% and 86.4%, compared to 64.2% and 68.2%, respectively, for the experienced group. For other colours, the percentage differences between the two groups were not as great as they were for red and green. It is interesting to note that more than half of the experienced participants selected the same meanings for red and green as the inexperienced participants, though the ratios decreased by 25% point. In interpreting the coloured pictorial displays and push-button switches, more than half of the experienced participants selected a different answer than the majority of inexperienced participants. Experienced participants interpreted the red pictorial display as an operating process and the green display as a shutdown process, and indicated that the red push-button switch was for operating a machine and the green push-button switch was for stopping a machine (Tables 6 and 7). Though most inexperienced participants interpreted the colours of displays and switches as per the safety guide or standard recommendations, the experienced participants interpreted the coloured displays and switches based on their practical use, even though more than half of them regarded red as proper for presenting danger/emergency and green as proper for presenting a normal state. It was shown that the experienced participants interpreted the colours of displays and controls of electric equipment differently from the general stereotypes of the colours, as the electrical equipment displays and controls were designed to emphasise the risk of electric shock when the equipment is operating. Even though the danger of electric shock can be represented by the red light, it was shown that inexperienced people tended to interpret it according to the general stereotype, presumably not understanding it to mean an electrical hazard warning. It is highly probable that a person can improperly operate an ECP and cause an accident if he or she has no knowledge or specific experience with ECPs. It is also noteworthy that even an experienced person’s interpretation of colours could conflict with the current meaning of the colours used in electrical equipment, which could result in human error when operating ECPs. The pictorial displays of pumping and coloured push buttons presented to the respondents are representative displays and controls of electrical equipment and they are hardly used in general purposed electronic devices. Therefore, many participants of the experienced group seemed to have preconceived notions about the meaning of the colours of the displays and controls, while many unexperienced participants interpreted the presented coloured displays and controls according to their general stereotypes. 5.
Conclusion
In electrical equipment, the red displays or switches are used to represent a normal state of operation and the green displays or switches are used to represent a shutdown state. This use of colours conflicts with colour stereotypes and the safety guidelines or standards regarding electrical equipment and machineries. Though there is a risk of electric shock, the general public are more likely to interpret the coloured displays and controls according to the general stereotypes, being unaware of the warning of risk. The current survey results indicated that there were significant differences between the inexperienced and experienced groups in interpreting the coloured displays and switches used in electrical equipment. The ECPs are mainly used by the specialised operators who are well aware of the colour meanings on the controls and displays. However, some ECPs are installed in public places where they can be easily accessed by inexperienced individuals who may misunderstand the colour’s meaning and improperly operate the equipment. Even though there are labels for each switch, it is still probable an accident attributed to human error could result from the conflict between the label and the colour. The result of this study showed that the colour codes of displays and controls used in ECPs conflict with the general stereotypes and it is necessary to redefine and redesign the colour coding system to enhance the usability and safety of ECPs. However, it may not be practical to change the colour design on the electrical equipment interfaces abruptly as it has
Ergonomics
9
been widely used and the operators are already accustomed to the current design and functions. It should be considerably investigated and prepared to find the effective measures to minimise the confusions to be caused by the change of colour coding system, if the colour design is to be changed. Therefore, a long-term study is recommended for the redesign of colour coding systems of electrical equipment. In the current state, it is necessary for the electric engineers to understand that the general public views these colours differently. It is strongly recommended that additional methods to inform the users of the colours’ meanings should be provided in designing ECPs, and it needs to put more efforts to emphasise that the green light is for turning off the equipment and the red light indicates a normal state of operation. Disclosure statement No potential conflict of interest was reported by the authors.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
References Borade, A. B., S. V. Bansod, and V. R. Gandhewar. 2008. “Hazard Perception Based on Safety Words and Colors: An Indian Perspective.” International Journal of Occupational Safety and Ergonomics 14: 407– 416. Braun, C. C., P. B. Kline, and N. C. Silver. 1995. “The Influence of Color on Warning Label Perceptions.” International Journal of Industrial Ergonomics 15 (3): 179– 187. doi:10.1016/0169-8141(94)00036-3. Braun, C. C., and N. C. Silver. 1995. “Interaction of Signal Word and Colour on Warning Labels: Differences in Perceived Hazard and Behavioural Compliance.” Ergonomics 38 (11): 2207– 2220. doi:10.1080/00140139508925263. Chan, A. H. S., and A. J. Courtney. 2001. “Color Associations for Hong Kong Chinese.” International Journal of Industrial Ergonomics 28 (3– 4): 165– 170. doi:10.1016/S0169-8141(01)00029-4. Chan, A. H. S., and A. W. Y. Ng. 2009. “Perceptions of Implied Hazard for Visual and Auditory Alerting Signals.” Safety Science 47 (3): 346– 352. doi:10.1016/j.ssci.2008.06.003. Chapanis, A. 1994. “Hazards Associated with Three Signal Words and Four Colours on Warning Signs.” Ergonomics 37 (2): 265– 275. doi:10.1080/00140139408963644. Chengalur, S. N., S. H. Rodgers, and T. E. Bernard. 2004. Kodak’s Ergonomic Design for People At Work. 2nd ed. Hoboken, NJ: John Wiley & Sons. Griffith, L. J., and S. D. Leonard. 1997. “Association of Colors with Warning Signal Words.” International Journal of Industrial Ergonomics 20 (4): 317– 325. doi:10.1016/S0169-8141(96)00062-5. Information Centre of the Korean Law. 1992. Law of Occupational Safety and Health, http://www.law.go.kr/ KATS (Korean Agency for Technology and Standards). 2012. “KS C IEC 60204-1, Safety of Machinery – Electrical Equipment of Machines – Part 1: General Requirements.”. KEPCO (Korea Electric Power Corporation). 2009. “Statistics of electric injures.” Konz, S., and S. Johnson. 2004. Work Design – Occupational Ergonomics. 6th ed. AZ, USA: Holcomb Hathaway. KOSHA (Korea Occupational Safety and Health Agency). 2011. “KOSHA Guide E-94-2011: Technical Safety Guideline for Electrical Devices of Industrial Machineries.” Kroemer, K. H. E., H. B. Kroemer, and K. E. Kroemer-Elbert. 1994. Ergonomics – How to Design for Ease and Efficiency. Prentice Hall, NJ, USA. Leonard, S. D. 1999. “Does Color of Warnings Affect Risk Perception?” International Journal of Industrial Ergonomics 23 (5 – 6): 499– 504. doi:10.1016/S0169-8141(98)00015-8. Mayhorn, C. B., M. S. Wogalter, J. L. Bell, and E. F. Shaver. 2004. “What Does Code Red Mean?” Ergonomics in Design 12 (4): 12. doi:10.1177/106480460401200404. Pravossoudovitch, K., F. Cury, S. G. Young, and A. J. Elliot. 2014. “Is Red the Colour of Danger? Testing an Implicit Red-Danger Association.” Ergonomics 57 (4): 503–510. doi:10.1080/00140139.2014.889220. Wickens, C. D., and J. G. Hollands. 2000. Engineering Psychology and Human Performance. 2nd ed. Prentice Hall, NJ, USA. Woodson, W. E., B. Tillman, and P. Tillman. 1992. Human Factors Design Handbook. 2nd ed., McGraw-Hill, NY, USA.
ISSN: 0014-0139 (Print) 1366-5847 (Online) Journal homepage: http://www.tandfonline.com/loi/terg20
Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels Inseok Lee & Won-Gue Hwang To cite this article: Inseok Lee & Won-Gue Hwang (2015): Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels, Ergonomics, DOI: 10.1080/00140139.2015.1047803 To link to this article: http://dx.doi.org/10.1080/00140139.2015.1047803
Accepted author version posted online: 15 May 2015. Published online: 19 Jun 2015. Submit your article to this journal
Article views: 46
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=terg20 Download by: [University of Pennsylvania]
Date: 05 November 2015, At: 15:56
Ergonomics, 2015 http://dx.doi.org/10.1080/00140139.2015.1047803
Effects of personal experiences on the interpretation of the meaning of colours used in the displays and controls in electric control panels Inseok Lee* and Won-Gue Hwang Department of Civil, Safety, and Environmental Engineering, Hankyong National University, 327 Jungang-ro, Anseong, Gyeonggi 456-749, South Korea
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
(Received 15 October 2014; accepted 29 April 2015) A survey was conducted to examine how personal experiences affect the interpretation of the meaning of display and control colours on electric control panels (ECPs). In Korea, the red light on ECPs represents a normal state of operation, while the green light represents a stopped state of operation; this appears to contradict the general stereotypes surrounding these colours. The survey results indicated that the participants who had experience in using ECPs interpreted the colour meaning differently from the other participant group. More than half of the experienced participants regarded the coloured displays and controls as they were designed, while most participants in the other group appeared to interpret the colours in accordance with the stereotypes. It is presumed that accidents related to human errors can occur when non-experienced people use the ECPs, which are easily accessible in many buildings. Practitioner Summary: A survey was conducted to investigate how personal experiences affect the interpretation of the function meanings of coloured lights on electrical control panels. It was found that the interpretation varies according to personal experiences, which can induce accidents related to human errors while operating electrical equipment. Keywords: stereotype of colour; colour display and control; push-button switch; electric control panels; personal experience
1.
Introduction
An electrical control panel (ECP) is installed in most electrical equipment or systems as a human-machine interface to allow operators to monitor the status of the systems and control the electricity supply to the systems. These systems include factory production lines, fire-fighting equipment, air-conditioning equipment, elevators, water-heating boiler systems and others. The ECP usually comprises several controls such as push-button switches, rotary switches or emergency switches, and pictorial displays representing the status of electrical equipment. An operator usually uses the ECP to monitor and control the systems. If the operator misunderstands the systems’ status or makes an error in controlling the equipment, it can result in an accident with injuries or economic loss. According to Korea’s electrical accident statistics, human error while using ECPs was cited as one of the main causes of electrical shock accidents (KEPCO 2009). An electrical shock accident can be so severe that it results in fatal injuries, though the occurrence rate is relatively low compared to other electrical accidents. It is necessary to decrease the probability of human error while using ECPs in order to reduce the loss from electrical shock accidents. Colour-lighted push-button switches are widely installed on ECPs. A colour light installed in the switch turns on when the switch is pushed, while the system simultaneously begins to operate or stop according to the switch function, such as ‘On’ or ‘Off’ (Figure 1). The switch is a mixed-up device to be used as both a control and a display. In the ECPs generally used in Korea, the red switch is used for ‘On’ or ‘Operating’ functions, the green switch for ‘Off’ or ‘Stop’ and the yellow switch for ‘Malfunction’ or ‘Reset’. This seems to conflict with colour stereotypes and the ergonomic recommendations for the use of colours. For the design of general purpose controls, the use of red is recommended to indicate ‘stop’, ‘danger’ or ‘off; green is used to indicate ‘go’, ‘safe’, or ‘on’ and yellow is used to indicate ‘caution’ or ‘marginal situation’ (Chengalur, Rodgers, and Bernard 2004; Konz and Johnson 2004; Wickens and Hollands 2000). In the design of display lights, red is recommended to indicate ‘malfunction’ or ‘emergency’; green to indicate ‘go’, ‘in tolerance’, ‘acceptable’ or ‘ready’ and yellow to indicate ‘delay’, ‘check’ or ‘caution’ (Kroemer, Kroemer, and Kroemer-Elbert 1994; Woodson, Tillman, and Tillman 1992). Many studies also showed that the colour red is positively associated with the meaning of danger and the colour green is positively associated with the meaning of safety (Chapanis 1994; Griffith and Leonard 1997; Leonard 1999; Chan and Courtney 2001; Borade, Bansod, and Gandhewar 2008; Chan and Ng 2009; Pravossoudovitch et al. 2014). According to Chan and Courtney
*Corresponding author. Email: [email protected] q 2015 Taylor & Francis
2
I. Lee and W.-G. Hwang
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Figure 1.
Colour-lighted push-button switches used on ECPs, which are red, green and yellow, respectively, from left to right.
(2001) who surveyed the associated meanings for various colours with Hong Kong Chinese participants, the colour red is mostly associated with ‘Stop’, ‘Caution’ and ‘Danger’ and the colour green is mostly associated with ‘Go’, ‘Safe’ and ‘On’. In Korea, there are guidelines and standards related to the use of colours in machinery controls and displays: the ‘KOSHA Guide E-94-2011: Technical safety guideline for electrical devices of industrial machineries’ and ‘KS C IEC 60241-1: Safety of machinery – Electrical equipment of machines – Part 1: General requirements’ (KOSHA 2011; KATS 2012). In these guidelines and standards, seven different colours are defined and recommended for switches used in electrical devices and five different colours are recommended for display lights (Tables 1 and 2). The recommendations for the colour meanings are similar to each other in that red is used for emergent situations, green for safe or normal situations and yellow for malfunctions. Meanwhile, in the Korean law of occupational safety and health, there is a regulation for the use of colours for safety and health codes or symbols (Information Centre of the Korean Law 2015). According to the regulation, red should be used for prohibition or warning symbols, yellow for caution, blue for instruction and green for guide. This regulation, however, is limited to the colours used for safety and health codes or symbols. Therefore, it cannot be directly applied to the colours of switches and displays on ECPs. As described, the red push-button switch on an ECP is used for operating the system, with the red light kept turning on while the system is operating. The green light is for stopping the system, with the green light kept turning on when the system is stopped. It is presumed that the red colour is used to indicate that while the system is operating, the electric current is flowing and there is a risk of electrical shock. The red light appears to be designated to remind the user of the electrical shock danger. On the other hand, the green light appears to be used to indicate a safe state, i.e. free from the electric shock, because the system is not operating and therefore, no electricity is flowing in the system. However, it is questionable as to whether individuals who are not accustomed to electrical equipment and are unfamiliar with the meaning of electrical hazard would interpret the meaning of the colours as they are designed. They might interpret the meaning of the colours in a more general way according to the stereotypes, which might result in an accident due to improper operation of electrical equipment. Although ECPs are devices meant to be used by specialised operators, there are many ECPs in modern buildings which are open to the public and generally accessible. Therefore, it is necessary to study how the colour codes in ECPs can be improperly interpreted and how this can be related to the possible occurrence of human errors. Colour is widely used as a communication mode in displays and controls because it is relatively easy and quickly recognised. However, caution should be used in assigning specific colours as codes with specific meanings as it is known that approximately 4 –8% of population has difficulty in perceiving some colours (Konz and Johnson 2004) and there are
Table 1.
Meanings of colours for push-button switches (KOSHA 2011).
Colour Meaning
Explanation
Examples
Red
Operating when a dangerous or emergent situation occurs Operating when malfunction or abnormal situation occurs
Stop switch for emergency
Emergency
Yellow Malfunction Green Blue White Grey Black
Safety Forceful action No specific meaning No specific meaning No specific meaning
Display for returning to normal states Display for re-operating stopped automatic functions Operating during normal state Possible to be used in a Start or On switch Operating when forcefully activating functions Switch for returning to normal states General functions of activation except emergent stops Activation (preferred) or Stop switch General functions of activation except emergent stops Activation or Stop switch General functions of activation except emergent stops Activation or Stop (preferred) switch
Ergonomics
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Table 2.
3
Meanings of colours for display lights (KOSHA 2011).
Colour
Meaning
Explanation
Examples
Red
Emergency
Dangerous or emergent situations
Yellow
Malfunction
Malfunction or abnormal states
Green
Safety
Normal state
Blue
Forceful action
White
Neutral
Response or the state of the operator’s operation Others
When measures such as pressure, temperature, etc. exceed the limit When measures such as pressure, temperature, etc. are out of the normal range When measures such as pressure, temperature, etc. are within the normal range Pointing to a predetermined value General information
some cultural or national differences in the stereotype of colours (Chan and Courtney 2001). In addition, when using colours as a tool to inform users of meanings, the colours should be considered to enhance the conceptual compatibility in order to decrease the probability of human error and increase the system’s usability. The use of colour with other types of display like symbols or labels can affect the perceptions of the designated meanings (Braun, Kline, and Silver 1995; Braun and Silver 1995; Leonard 1999; Mayhorn et al. 2004). The current colour codes used in ECPs appear to conflict with the colour stereotype. It would be useful to understand how the personal experiences affect the interpretation of the colour-lighted switches on ECPs in an effort to decrease human error when using electrical equipment and prevent electrical shock accidents. In this study, a survey was conducted to examine how personal experiences correlate with the interpretation of the meaning of colours used in electrical devices, pictorial displays and push-button switches.
2. Method 2.1 Participants and survey methods In this study, 350 participants (318 males and 32 females) were surveyed to examine the interpretation of the meaning of the colours used in the controls and displays of electrical equipment. The pool of randomly selected participants comprised employees from several different companies, including some related to electrical equipment operation, and university students primarily from the faculty of engineering. The participants were interviewed and informed of the survey’s purpose by the researcher before they responded to the questionnaire. It took participants less than thirty minutes to complete the questionnaire. The questionnaire included the following topics: . General information: major or occupation . Experience in using ECPs and push-button switches . Proper meaning of the coloured button switches used in electrical equipment. Seven colours were presented: red, green, yellow, blue, white, grey and black. The participants were asked to select the most appropriate meaning for each coloured button switch from the following: ‘emergency (including dangerous state or emergent operation)’, ‘abnormal state’, ‘normal state (including normal operation)’, ‘necessity of forceful operation’, ‘no specific meaning’ and ‘unknown’. . Interpretation of the coloured pictorial display representing a pumping process. Two pictorial displays representing pumping processes were presented in red and green respectively (Figure 2). The participants were asked to select whether each picture represented an ‘operating state’ or ‘stopped state’.
Figure 2. A pictorial display representing the process state used in the questionnaire (The circular part around character ‘A’ was coloured as red or green).
4
I. Lee and W.-G. Hwang . Interpretation of the colour-lighted push-button switches. Three push-button switches in red, green and yellow respectively were presented. The participants were asked to select the function meaning for each switch from the choices of ‘operating’, ‘stop’, ‘abnormal/reset’.
2.2
Analysis
The participants were classified into two groups according to their majors, occupations and experience in using ECPs. Chisquare tests with a significance level of 0.05 were used to analyse the correlations between the participants’ characteristics and their responses to the questions on the electrical device switch colour meanings, the pictorial displays colour meanings and the push-button switch colour meanings. SAS (ver. 9.2) was used in the statistical analyses.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
3. Results 3.1 General characteristics of participants The participants’ ages were balanced across the following ranges: 20s (40.6%), 30s (32.0%) and 40s (23.4%). With regard to their occupations, 57.4% of the participants were employees, while 31.4% were university students and 11.1% were selfemployed or owners of small businesses. Ninety-eight participants (28.0%) studied in fields related to electrical engineering in high school or university, while the remainder studied in other fields. Most participants studied engineering or natural sciences, only 8.0% of the participants studied humanities, literature or social sciences (Table 3). One hundred and forty-four participants (41.1%) worked in occupations related to the operation of electrical equipment or machineries, while the remainder of the participants worked in unrelated fields or were students. 3.2 Experience with ECPs and push-button switches Approximately half of the participants (49.4%) answered that they had experience in using ECPs (Table 3). The ratio of the experience was found to be statistically correlated to the participants’ majors and occupations ( p , 0.05). The electrical engineering participants indicated a higher experience rate than participants not in electrical engineering (76.5% vs. 38.9%). The participants who were in occupations related to the electrical equipment or machineries also indicated a higher experience rate than the others (89.6% vs. 21.4%). 3.3
Interpretation of colours used for electrical equipment switches
The participants were asked to select the most appropriate meaning of each colour used for electrical equipment or machinery switches. The responses indicated that 77.4% of the participants selected emergent situation for red and normal state for green, and 71.4% selected abnormal situation for yellow (Table 4). For white, grey and black, most participants responded that they thought there was no specific proper meaning or that they were unaware the proper meanings (86.3 –95.1%). For blue, while more than half of the participants selected no-specific meaning or that the proper meaning was unknown (59.7%), a substantial number of participants selected mandatory operation or forceful operation (29.7%). The participants’ selections for the most appropriate meaning for the red, green, yellow and blue switches were found to be significantly correlated to their majors, occupations and experiences in using ECPs, respectively ( p , 0.05) (Tables 5). Among the electrical engineering participants, 64.3% selected emergent situation and 23.5% selected normal situation as the most appropriate meaning for the red switch, while 82.5% of the remaining participants selected emergent situation as Table 3.
Number (percentage) of participants categorised by their majors and occupations vs. experience in using ECPs (People, %). Use of ECP
Major
Electric Eng. Non-Electric Equip. Others
Occupation Total
Exp
No Exp
75 (76.5) 98 (38.9) 129 (89.6) 44 (21.4) 173 (49.4)
23 (23.5) 154 (61.1) 15 (10.4) 162 (78.6) 177 (50.6)
Total 98 (28.0) 252 (72.0) 144 (41.1) 206 (58.9) 350 (100.0)
(100.0) (100.0) (100.0) (100.0) (100.0)
Ergonomics
5
Table 4. Percentage of participants selecting the most appropriate meaning of the colours for switches on electrical equipment or machineries (%). Meanings Emergency situation Abnormal situation Normal situation Forceful operation Not specified / unknown Total
Red
Green
Yellow
Blue
White
grey
Black
77.4 1.4 12.9 0.9 7.4 100.0
0.3 1.4 77.4 2.6 18.3 100.0
6.6 71.4 0.9 4.0 17.1 100.0
0.0 1.7 9.4 29.1 59.7 100.0
0.6 2.6 0.6 10.0 86.3 100.0
0.3 2.6 0.0 2.6 94.6 100.0
0.0 1.7 0.3 2.9 95.1 100.0
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Note: The highest percentage for each colour is noted as bold.
the most appropriate meaning for red. For the green switch, the ratios of participants who selected normal situation were 69.4% of those with electrical engineering backgrounds and 80.6% of the remaining participants. Approximately a quarter of the electrical engineering participants answered that that there was no specific meaning or they did not know the meaning of the green switch. For yellow switch, the difference in meaning interpretation between the electrical engineering participants and the remaining participants was not as large as the differences in the green or red switches. For blue, the percentage of participants who selected mandatory or forceful operation was higher for the non-electrical engineering group than for the electrical engineering group (32.5% vs. 20.4%). The participants whose occupations were not related to electrical equipment operation or maintenance mostly regarded the red switch as proper for an emergent situation (82.5%), while the ratio decreased to 64.3% with the participants whose occupations are related to electrical equipment. For green switch, similar percentage results were shown for the normal situation. It is interesting to note that 26.5% of the participants whose occupations are related to electrical equipment answered that there is no specific meaning or the meaning was unknown. The most participants without experience in using ECPs believed that the red switch was proper for an emergent situation (90.4%), while of the experienced participants 64.2% indicated it was for emergent situations and 23.7% indicated it was for normal situations. The results for the green switch indicated a similar percentage pattern, with 23.6% of the experienced participants answering that there was no specific meaning or the meaning was unknown. Table 5.
Percentage of participants selecting the most appropriate meaning of the colours for displays and controls on ECPs (%).
Characteristic
Colour
Majors
Red Green Yellow Blue
Occupations
Red Green Yellow Blue
Experience
Red Green Yellow Blue
Group
Emergency situation
Abnormal situation
Normal situation
Forceful operation
Not Specified/Not knowing
Total
Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric
64.3 82.5 0.0 0.4 11.2 4.8 0.0 0.0
0.0 2.0 3.1 0.8 67.3 73.0 1.0 2.0
23.5 8.7 69.4 80.6 0.0 1.2 5.1 11.1
2.0 0.4 1.0 3.2 1.0 5.2 20.4 32.5
10.2 6.3 26.5 15.1 20.4 15.9 73.5 54.4
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Equip. Others Equip. Others Equip. Others Equip. Others
59.7 89.8 0.7 0.0 13.2 1.9 0.0 0.0
2.1 1.0 2.8 0.5 67.4 74.3 2.1 1.5
27.8 2.4 64.6 86.4 0.0 1.5 5.6 12.1
2.1 0.0 2.1 2.9 2.8 4.9 18.1 36.9
8.3 6.8 29.9 10.2 16.7 17.5 74.3 49.5
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp. Exp. No Exp. Exp. No Exp.
64.2 90.4 0.6 0.0 11.6 1.7 0.0 0.0
2.3 0.6 2.3 0.6 68.8 74.0 2.9 0.6
23.7 2.3 68.2 86.4 0.0 1.7 7.5 11.3
1.7 0.0 2.3 2.8 2.9 5.1 22.0 36.2
8.1 6.8 26.6 10.2 16.8 17.5 67.6 52.0
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Note: The highest percentage in each row is noted as bold.
6
I. Lee and W.-G. Hwang
Table 6.
Percentage of participants selecting the proper meaning of the coloured pictorial displays of a pumping process (%).
Characteristic
Colour
Majors
Red Green
Jobs
Red Green
Experiences
Red Green
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
Total
Group
Operating state (ON)
Stopped state (OFF)
Total
Electric Eng. Non-electric Electric Eng. Non-electric
52.6 30.9 48.5 70.4
47.4 69.1 51.5 29.6
100.0 100.0 100.0 100.0
Equip. Others Equip. Others
61.4 20.0 38.6 82.0
38.6 80 61.4 18.0
100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp.
54.1 20.0 45.9 82.4 37.1 64.1
45.9 80.0 54.1 17.6 62.9 35.9
100.0 100.0 100.0 100.0 100.0 100.0
Red Green
Note: The highest percentage in each row is noted as bold.
3.4 Interpretation of colours for a pictorial symbol of a process In the selection of the proper meanings for the red and green pictorials representing a pumping process, 62.9% of the participants interpreted the red picture to represent a stopped process and 64.1% interpreted the green picture represent an operating process (Table 6). The participants’ interpretations of the red and green pictorial meanings were found to be significantly correlated to their majors, occupations and experiences in using ECPs ( p , 0.05) (Table 6). Among the participants whose majors are related to electrical engineering, 52.6% of the participants interpreted the red picture to indicate an operating process and 51.5% interpreted the green picture to indicate a shutdown process. In the other group, however, 69.1% of the participants interpreted the green picture to indicate an operating process and 70.4% interpreted the red picture to indicate a shutdown process. Based on occupations, the red picture was interpreted as an operating process by 61.4% of the participants in an occupation related to electrical equipment operation or maintenance, while 80.0% of the other participant group interpreted it to indicate a shutdown process. The results for the green picture were inversely similar to the results for the red picture. Similar differences in results between the experienced and inexperienced participants were attained for the interpretation of the coloured pictorials. Most inexperienced participants regarded the red picture to indicate a stopped operation (80.0%), while 54.1% of the experienced participants regarded it as being in an operating state. Interpretations of the green picture were inversed from the results of the red picture. 3.5
Interpretation of colours for push-button switches on ECPs
With regard to the proper meanings for the red, green and yellow-lighted push-button switches generally used on ECPs, 60.3% of the participants thought the red light was to stop the equipment, 67.1% selected the green light was to operate the equipment and 93.2% thought the yellow light indicated an abnormal equipment state or to be reset (Table 7). It was found that the participants’ selection of the colours’ functions or meanings was significantly correlated to their majors, occupations and experiences in using ECPs ( p , 0.05). According to the participants’ majors, 52.1% of the electrical engineering participants indicated the red light was to operate the equipment and the green light was to stop it, while 65.6% of the other group indicated that the red lighted was to stop the equipment and 74.6% indicated the green light was to operate it. The majority of participants from both groups regarded the yellow light to indicate abnormal equipment situations or the need to reset. The majority of participants in occupations unrelated to the operation or maintenance of electrical equipment regarded the red switch for stopping equipment (76.8%), while 61.3% of the participants in occupations related to electrical equipment operation or maintenance indicated it was for operating equipment. For the green switch, the results were reversed with 59.9% of the participants in occupations related to electrical equipment regarding it as a stopping function and 86.4% of the other group regarding it as an operating function. It was found that experience with using ECPs had the most differentiated effect on the selection of the coloured switch functions. For the red switch, 76.3% of the non-experienced participants selected stopping equipment and 52.6% of the experienced participants selected operating equipment. For the green switch, 85.8% of the non-experienced participants selected operating equipment and 51.5% of the experienced participants selected stopping equipment.
Ergonomics Table 7.
Percentage of participants selecting the most appropriate meaning of the colours for push-button switches (%).
Characteristic
Colour
Majors
Red Green Yellow
Occupations
Red Green Yellow
Experience
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
7
Red Green Yellow
Total
Group
Operate
Stop
Abnormal/Reset
Total
Electric Eng. Non-electric Electric Eng. Non-electric Electric Eng. Non-electric
52.1 26.2 47.9 74.6 0.0 0.4
46.9 65.6 52.1 24.6 1.0 8.6
1.0 8.2 0.0 0.8 99 91
100.0 100.0 100.0 100.0 100.0 100.0
Equip. Others Equip. Others Equip. Others
61.3 13.6 40.1 86.4 0.0 0.5
37.3 76.8 59.9 12.6 1.4 10.1
1.4 9.6 0.0 1.0 98.6 89.4
100.0 100.0 100.0 100.0 100.0 100.0
Exp. No Exp. Exp. No Exp. Exp. No Exp.
52.6 14.2 48.5 85.8 0.6 0.0 33.5 67.1 0.3
44.4 76.3 51.5 13.0 2.9 10.1 60.3 32.4 6.5
2.9 9.5 0.0 1.2 96.5 89.9 6.2 0.6 93.2
100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Red Green Yellow
Note: The highest percentage in each row is noted as bold.
4.
Discussion
In this study, a survey was conducted to examine the relationship between personal experiences and the understanding of the meaning of switch colours used in electrical equipment. The three main subjects of the questionnaire were (1) how the participants understood the meanings of the switch colours, (2) how the participants interpreted the two different coloured pictorial displays representing a pumping process, (3) and how the participants interpreted the three main colours of the push-button switches widely used on ECPs in Korea. The participants were grouped by their personal experiences including major in school, relation of occupation to the operation of electrical equipment and experiences in using ECPs. The groups were compared in terms of their responses to the questions. 4.1
Interpretation of the meaning of colours for the controls and displays
The participants were asked to select the most appropriate meanings for the seven colours recommended for electrical equipment controls in Korean safety guides or standards (KOSHA 2011; KATS 2012): red, green, yellow, blue, white, grey and black. The majority of participants answered that red was proper for representing emergency or danger, green represented a normal state and yellow represented an abnormal state (71.4 –77.4%). For white, grey and black, most participants answered that there was no specific proper meaning for those colours or they were unaware of their proper meanings (86.3 –95.1%). These results coincided with recommendations in the KOSHA Guide E-94-2011 and KS C IEC 60204-1:2012 as shown in Table 1 and ergonomics literatures (Chengalur, Rodgers, and Bernard 2004; Konz and Johnson 2004; Wickens and Hollands 2000). The only exception was the interpretation of the meaning of blue. The blue switch is recommended as a forceful operation function, which was supported by only 29.1% of the participants, while 59.7% of the participants selected ‘no specific meaning’ or ‘unknown meaning’. Based on this result, one should be cautious when employing a blue switch to indicate a forceful operation or resetting function on machinery or electrical equipment. The participants’ interpretations of the red and green pictorial displays representing a pumping process were found to be more diverse than the selection of the most appropriate meaning of the seven different colours. Though more than half of the participants regarded the red picture as representing a stopped process and the green picture as representing an operating process (62.9% and 64.1%), it is interesting to note that a substantial number of respondents inversely interpreted the two coloured displays, i.e. 37.1% regarded the red pictorial as representing an operating process and 35.9% thought the green pictorial as representing a stopped process. The participants’ results were also similar for the interpretation of the meaning of the colour-lighted push-button switches; 60.3% of the participants believed that the red light was for turning off the equipment and 67.1% believed the green light was for operating the equipment, while the others interpreted the colours differently. This diverse interpretation of colours indicates that in order to inform the users of the meanings of colours used
8
I. Lee and W.-G. Hwang
for displays and controls, additional methods such as labels or legends should be applied in order to prevent human error related to misunderstanding the colours’ purposes.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
4.2
Personal experiences and interpretation of the meaning of colours for the controls and displays
The participants were grouped into two groups according to three different criteria: whether or not their major was related to electric engineering; whether or not their occupation was related to electrical equipment operation and whether or not the participant had the experience in using ECPs. The criteria were determined to be correlated. As shown in Table 3, the experienced participants tended to have studied electrical engineering and tended be in an occupation related to the electrical equipment operation. Therefore, the relationships between these personal experiences and the interpretation of the colours revealed similar patterns, though there are some differences in the percentages (Tables 5 –7). In the selection of the proper meaning of the colours for the controls of electric equipment, the percentages of inexperienced participants who selected danger/emergency for red and normal state for green were 90.4% and 86.4%, compared to 64.2% and 68.2%, respectively, for the experienced group. For other colours, the percentage differences between the two groups were not as great as they were for red and green. It is interesting to note that more than half of the experienced participants selected the same meanings for red and green as the inexperienced participants, though the ratios decreased by 25% point. In interpreting the coloured pictorial displays and push-button switches, more than half of the experienced participants selected a different answer than the majority of inexperienced participants. Experienced participants interpreted the red pictorial display as an operating process and the green display as a shutdown process, and indicated that the red push-button switch was for operating a machine and the green push-button switch was for stopping a machine (Tables 6 and 7). Though most inexperienced participants interpreted the colours of displays and switches as per the safety guide or standard recommendations, the experienced participants interpreted the coloured displays and switches based on their practical use, even though more than half of them regarded red as proper for presenting danger/emergency and green as proper for presenting a normal state. It was shown that the experienced participants interpreted the colours of displays and controls of electric equipment differently from the general stereotypes of the colours, as the electrical equipment displays and controls were designed to emphasise the risk of electric shock when the equipment is operating. Even though the danger of electric shock can be represented by the red light, it was shown that inexperienced people tended to interpret it according to the general stereotype, presumably not understanding it to mean an electrical hazard warning. It is highly probable that a person can improperly operate an ECP and cause an accident if he or she has no knowledge or specific experience with ECPs. It is also noteworthy that even an experienced person’s interpretation of colours could conflict with the current meaning of the colours used in electrical equipment, which could result in human error when operating ECPs. The pictorial displays of pumping and coloured push buttons presented to the respondents are representative displays and controls of electrical equipment and they are hardly used in general purposed electronic devices. Therefore, many participants of the experienced group seemed to have preconceived notions about the meaning of the colours of the displays and controls, while many unexperienced participants interpreted the presented coloured displays and controls according to their general stereotypes. 5.
Conclusion
In electrical equipment, the red displays or switches are used to represent a normal state of operation and the green displays or switches are used to represent a shutdown state. This use of colours conflicts with colour stereotypes and the safety guidelines or standards regarding electrical equipment and machineries. Though there is a risk of electric shock, the general public are more likely to interpret the coloured displays and controls according to the general stereotypes, being unaware of the warning of risk. The current survey results indicated that there were significant differences between the inexperienced and experienced groups in interpreting the coloured displays and switches used in electrical equipment. The ECPs are mainly used by the specialised operators who are well aware of the colour meanings on the controls and displays. However, some ECPs are installed in public places where they can be easily accessed by inexperienced individuals who may misunderstand the colour’s meaning and improperly operate the equipment. Even though there are labels for each switch, it is still probable an accident attributed to human error could result from the conflict between the label and the colour. The result of this study showed that the colour codes of displays and controls used in ECPs conflict with the general stereotypes and it is necessary to redefine and redesign the colour coding system to enhance the usability and safety of ECPs. However, it may not be practical to change the colour design on the electrical equipment interfaces abruptly as it has
Ergonomics
9
been widely used and the operators are already accustomed to the current design and functions. It should be considerably investigated and prepared to find the effective measures to minimise the confusions to be caused by the change of colour coding system, if the colour design is to be changed. Therefore, a long-term study is recommended for the redesign of colour coding systems of electrical equipment. In the current state, it is necessary for the electric engineers to understand that the general public views these colours differently. It is strongly recommended that additional methods to inform the users of the colours’ meanings should be provided in designing ECPs, and it needs to put more efforts to emphasise that the green light is for turning off the equipment and the red light indicates a normal state of operation. Disclosure statement No potential conflict of interest was reported by the authors.
Downloaded by [University of Pennsylvania] at 15:56 05 November 2015
References Borade, A. B., S. V. Bansod, and V. R. Gandhewar. 2008. “Hazard Perception Based on Safety Words and Colors: An Indian Perspective.” International Journal of Occupational Safety and Ergonomics 14: 407– 416. Braun, C. C., P. B. Kline, and N. C. Silver. 1995. “The Influence of Color on Warning Label Perceptions.” International Journal of Industrial Ergonomics 15 (3): 179– 187. doi:10.1016/0169-8141(94)00036-3. Braun, C. C., and N. C. Silver. 1995. “Interaction of Signal Word and Colour on Warning Labels: Differences in Perceived Hazard and Behavioural Compliance.” Ergonomics 38 (11): 2207– 2220. doi:10.1080/00140139508925263. Chan, A. H. S., and A. J. Courtney. 2001. “Color Associations for Hong Kong Chinese.” International Journal of Industrial Ergonomics 28 (3– 4): 165– 170. doi:10.1016/S0169-8141(01)00029-4. Chan, A. H. S., and A. W. Y. Ng. 2009. “Perceptions of Implied Hazard for Visual and Auditory Alerting Signals.” Safety Science 47 (3): 346– 352. doi:10.1016/j.ssci.2008.06.003. Chapanis, A. 1994. “Hazards Associated with Three Signal Words and Four Colours on Warning Signs.” Ergonomics 37 (2): 265– 275. doi:10.1080/00140139408963644. Chengalur, S. N., S. H. Rodgers, and T. E. Bernard. 2004. Kodak’s Ergonomic Design for People At Work. 2nd ed. Hoboken, NJ: John Wiley & Sons. Griffith, L. J., and S. D. Leonard. 1997. “Association of Colors with Warning Signal Words.” International Journal of Industrial Ergonomics 20 (4): 317– 325. doi:10.1016/S0169-8141(96)00062-5. Information Centre of the Korean Law. 1992. Law of Occupational Safety and Health, http://www.law.go.kr/ KATS (Korean Agency for Technology and Standards). 2012. “KS C IEC 60204-1, Safety of Machinery – Electrical Equipment of Machines – Part 1: General Requirements.”. KEPCO (Korea Electric Power Corporation). 2009. “Statistics of electric injures.” Konz, S., and S. Johnson. 2004. Work Design – Occupational Ergonomics. 6th ed. AZ, USA: Holcomb Hathaway. KOSHA (Korea Occupational Safety and Health Agency). 2011. “KOSHA Guide E-94-2011: Technical Safety Guideline for Electrical Devices of Industrial Machineries.” Kroemer, K. H. E., H. B. Kroemer, and K. E. Kroemer-Elbert. 1994. Ergonomics – How to Design for Ease and Efficiency. Prentice Hall, NJ, USA. Leonard, S. D. 1999. “Does Color of Warnings Affect Risk Perception?” International Journal of Industrial Ergonomics 23 (5 – 6): 499– 504. doi:10.1016/S0169-8141(98)00015-8. Mayhorn, C. B., M. S. Wogalter, J. L. Bell, and E. F. Shaver. 2004. “What Does Code Red Mean?” Ergonomics in Design 12 (4): 12. doi:10.1177/106480460401200404. Pravossoudovitch, K., F. Cury, S. G. Young, and A. J. Elliot. 2014. “Is Red the Colour of Danger? Testing an Implicit Red-Danger Association.” Ergonomics 57 (4): 503–510. doi:10.1080/00140139.2014.889220. Wickens, C. D., and J. G. Hollands. 2000. Engineering Psychology and Human Performance. 2nd ed. Prentice Hall, NJ, USA. Woodson, W. E., B. Tillman, and P. Tillman. 1992. Human Factors Design Handbook. 2nd ed., McGraw-Hill, NY, USA.
