Effects of sign design features and training on comprehension of traffic signs in Taiwanese and Vietnamese user groups

International Journal of Industrial Ergonomics 42 (2012) 1e7

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Effects of sign design features and training on comprehension of traffic signs in Taiwanese and Vietnamese user groups Yang-Kun Ou, Yung-Ching Liu* Department of Industrial Engineering and Management, National Yunlin University of Science and Technology, 123, Section 3, University Road, Touliu, Yunlin 640, Taiwan, ROC

a r t i c l e i n f o

a b s t r a c t

Article history: Received 7 January 2010 Received in revised form 6 June 2011 Accepted 28 August 2011 Available online 15 October 2011

This study examined the effects of sign design features and training on the comprehension of four types of Taiwanese traffic signs in Taiwanese and Vietnamese users. Thirty Taiwanese and thirty Vietnamese, each group gender-balanced, participated in this experiment, which involved 5 design features (familiarity, concreteness, simplicity, meaningfulness, and semantic closeness), 4 types of traffic signs (warning, prohibition, auxiliary, and indicatory), and 3 training conditions (before training, immediately following training, and one month after training). A total of sixty-five traffic signs were selected as the stimuli and each was presented on a 10 cm
10 cm white cardboard in random order. Within each training condition participants were instructed to (1) verbally describe their comprehension of the meaning of the signs, which was then evaluated by the experimenter from 0 to 1, and (2) provide subjective ratings for each of the five design features, on a scale ranging from 0 to 100. The results reveal the training effect to be positive in both user groups. For Taiwanese, the average comprehension was 0.63 before training and it increased to 0.98 immediately after training. For Vietnamese, the average comprehension was 0.41 before training and it increased to 0.89 immediately after training. Even one month after the training had taken place, the comprehension scores of both groups were still higher than groups that did not receive training (Taiwanese group: 0.83; Vietnamese group: 0.66). For the two groups, the design features of concreteness and meaningfulness were highly correlated (Taiwanese group: r ¼ 0.97; Vietnamese group: r ¼ 0.95), and the feature of semantic closeness had the greatest positive correlation with comprehension (Taiwanese group: r ¼ 0.88; Vietnamese group: r ¼ 0.80). In addition, a drop correlated to comprehension was found to be significant (Taiwanese group: r ¼ 0.92; Vietnamese group: r ¼ 0.89), and semantic closeness was the most negatively correlated feature (Taiwanese group: r ¼ 0.82; Vietnamese group: r ¼ 0.60), meaning that, the closer the semantic meaning is to the sign design, the higher the comprehension and the less decline in sign comprehension. Relevance to industry: Globalization means that a country must cater to a population with a diversity of cultural backgrounds. Designing signs that effectively convey safety information to all the different groups of users has thus become an important issue. This research attempts to investigate the relationship between sign design feature and training on traffic sign comprehension in Taiwanese and Vietnamese users. The results of this study can provide insight into designing public signs and can be extended to various instructional pictures provided with consumer products designed for world-wide use. Ó 2011 Elsevier B.V. All rights reserved.

Keywords: Comprehension Sign Design features Traffic sign Training

1. Introduction Traffic signs are a necessary means of communicating information to traffic, serving as a reminder, direction, or warning. The design of traffic signs should allow users to precisely and effectively

* Corresponding author. Tel.: þ886 5 5342601x5124; fax: þ886 5 531 2073. E-mail address: [email protected] (Y.-C. Liu). 0169-8141/$ e see front matter Ó 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.ergon.2011.08.009

comprehend the correct information in order to avoid conflicts or accidents in a changing traffic environment. Through in-depth analysis of 77 traffic accidents, Malaterre (1990) found that neglect of road users and incorrect comprehension of traffic signs are the major human errors in traffic accidents. The different recognition of traffic signs among road users is one of the critical factors leading to traffic accidents (Retting et al., 2003; Massie et al., 1993). In recent years, Taiwan has been employing a large number of foreign workers: foreign workers make up 3% of the total

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population and most of them are come from Southeast Asian countries (ie. Indonesia, Vietnam and the Philippines). The biggest group of foreign workers is Indonesian workers, accounting for 40.8% of the foreign workers employed, and the second is Vietnamese workers, accounting for 21.2% (NIA, 2010). Road users with different cultural backgrounds and languages may often be confused by or misunderstand the traffic signs. Thus, it is important to probe into the differences between foreigners’ and local peoples’ traffic sign recognition and comprehension in Taiwan in searching for ways to improve the understanding of traffic signs and provide better user education. Different groups of users will show varying comprehension of signs, depending on their culture, conceptual compatibility, consistency, and familiarity (Piamonte, 2000; Shinar et al., 2003). Cairney and Sless (1982) found that different groups (i.e., Australians and Vietnamese) demonstrated different recognition and recall with regard to industrial-safety signs; compared to the foreigners (the Vietnamese), the local people (the Australians) had higher degrees of recognition and recall. The cause of these higher degrees of recognition and recall can be attributed to differences in environment, living habits, and culture. Choong and Salvendy (1998) studied the cognitive precision and reaction time on computer alphanumeric, pictorial, and combined modes in two groups, Americans and Chinese. They found that the Americans responded better to the alphanumeric mode than pictorial mode, whereas the Chinese showed the opposite response. Research on Canadian students showed that they did not fully comprehend the signs encountered during their trips in Europe, and their sign comprehension was significantly different to that of locals (Dewar and Ells, 1977). We have hypothesized that the comprehension of the Taiwanese would be better than the Vietnamese. The issue of different groups’ different comprehensions of traffic signs can be resolved by training (Lesch, 2003). Training can enhance the users’ comprehension of “automobile instrument panel signs,” “airport safety signs,” “industrial-safety signs,” and “pharmaceutical signs” (Ramakrishnan et al., 1999; Wogalter et al., 1997; Green and Pew, 1978). Green and Pew (1978) investigated the comprehension of automobile instrument panel signs. In the experiment, in which nineteen signs were used to examine the average errors among 20 participants, the researchers found that the participants demonstrated fewer incorrect recognitions after training (1.3 errors) than before training (7.1 errors). Wogalter et al. (1997) studied comprehension differences of pharmaceutical and industrial-safety signs before and after training. They found that, with regard to difficult signs, that is, pharmaceutical and industrialsafety signs, comprehension before the training was 54% for the former and 34% for the latter, but improved to 87% and 63% respectively six months after training. Moreover, there was no decline in memory for about one week after training. Ramakrishnan et al. (1999) studied the differences in comprehension and reaction time on airport safety signs before and after training. This experiment was a 3-stage experiment, including before training, immediately following training, and one month after training. The participants’ comprehension and reaction time for pictorial signs were enhanced after recognition and recall training. Moreover, after training, the rate of comprehension decline is said to be slower (Wang and Chi, 2003). Consequently, we hypothesized that training would improve our comprehension. The measurement of a sign’s design is based on the recognition rate. McDougall et al. (1999) defined five features as criteria for measuring sign design: familiarity, concreteness, complexity, meaningfulness, and semantic distance. In order to build a consistent order of response scales, we used the definitions of sign design features proposed by Ng and Chan (2007a,b, 2009), and changed complexity and semantic distance to simplicity and semantic

closeness, respectively. Concreteness means the sign depict objects which have obvious connections with the real world - abstract signs do not do this; better signs are more concrete, whereas ambiguous signs are difficult to understand (Wolff and Wogalter, 1993; Passini et al., 2008). Simplicity means the sign contains few elements or little detail - complex signs contain a lot of detail or are intricate. Dewar (1999) noted that simple signs are better than complicated ones with regard to comprehension. Meaningfulness refers to people’s comprehension of the meanings of a sign, and is regarded as an important characteristic of design (Huang et al., 2002; Lin, 1992). More meaningful signs will have higher guessability scores (Preece et al., 1994). Familiarity means the frequency of encounter or use in people’s daily lives. Rosson (2002) noted that designers should try to design signs that users are familiar with. The users would then comprehend these signs. Semantic closeness refers to the closeness of the relationship between what is depicted in the sign and the function it is intended to represent. Chan and Ng (2010) evaluated industrial-safety signs design using concreteness, simplicity, meaningfulness, familiarity, and semantic closeness as criteria and found that the correlation between semantic closeness and guessability score is the most significant. Lesch (2008) has suggested that the comprehension of sign characteristics examined more closely is higher than comprehension on post-training. Through these sign design characteristics, the comprehension of signs by different groups can be effectively probed, and the influence of these characteristics on comprehension can be studied. This study aimed to probe the following: (1) the difference in comprehension ability with respect to traffic signs among different nationalities. According to previous studies, training effectively improves the comprehension of foreigners; (2) the effect of training on sign comprehension in different user groups based on development trends in Taiwan; and (3) understanding the usefulness of the results of this study in providing design guidelines for traffic signs and other signs. 2. Methods 2.1. Participants Thirty Taiwanese and thirty Vietnamese participants were recruited to participate in this study. The Taiwanese group in this experiment was composed of 15 males and 15 females between the ages of 19 and 29 years (mean ¼ 22.1, S.D. ¼ 2.75). The Vietnamese group was composed of 15 males and 15 females between the ages of 21 and 26 years (mean ¼ 21.1, S.D. ¼ 1.41). All of the Vietnamese students were already in Taiwan for about 1e2 months, lived in a dorm and did not have any cars or motorcycles. The visual acuity for all groups was at least 0.8 and had to pass the Ishihara color blindness test. Al-Madani and Al-Janahi, (2002) found that people of different education levels have a different ability in terms of understanding traffic signs. Thus, this study restricted the sample to those with an undergraduate education. 2.2. Apparatus There are 203 traffic signs in Taiwan including 50 warning signs, 75 prohibition signs, 63 indicatory signs and 15 auxiliary signs. The traffic signs used in this study were adapted from the road traffic safety portal site of the Ministry of Transportation and Communications, Taiwan (RTSP, 2008). There are some differences in the traffic signs in Taiwan and Vietnam. For example, the background color of prohibition signs is white in Taiwan, but yellow in Vietnam. Furthermore, some of the signs used in this study do not exist in Vietnam, such as lane forbids entry, snow chains required, heavy motorbikes (above 500cc) forbidden entry, and empty taxis

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forbidden entry. This study selected 70 common traffic signs for the experiment, but five of them were used only for the practice sessions. The 65 signs used in the experiment included 24 warning signs, 28 prohibition signs, 9 indicatory signs and 4 auxiliary signs. The 65 traffic signs were not all pictorials. Five of them included Chinese characters, English characters, or numeric numbers, and each was printed on 10 cm
10 cm white cardboard (see Appendix). In addition, 65 cardboards were generated, each containing a text description of one of the pictorial signs. Wogalter et al. (1997) used filler tasks to prevent the confounding influence of participants’ short-term memory. In this study, the participants played a poker game to prevent rehearsal and memorization. 2.3. Experimental design Three factors were studied in this experiment, namely, country of origin (Taiwanese vs. Vietnamese, between-subjects), traffic signs (warning signs vs. prohibition signs vs. auxiliary signs vs. indicatory signs, within-subjects), and training (before training vs. immediately following training vs. one month after training, within-subjects). This study used an open-ended method to assess comprehension ability. Wolff and Wogalter (1998) recommended adopting this testing method because multiple-choice tests directly guide the subject’s sign recognition ability, thus greatly influencing the evaluation of comprehension. 2.4. Procedures All subjects who passed the visual exam provided their consent to participate in this experiment. Each participant was allowed to practice five traffic signs that were not included in the formal experimental trial. The purpose of the practice trials was to ensure that the participants could totally understand the contents and processors of the experiment in order to rate their cognitive responses consistently. Participants were instructed to (1) verbally describe the meanings of each traffic sign and (2) provide subjective ratings for each of the five design features on a scale of 0e100. The ratings were based on concreteness (0 ¼ definitely abstract, 100 ¼ definitely concrete), simplicity (0 ¼ very complex, 100 ¼ very simple), meaningfulness (0 ¼ completely meaningless, 100 ¼ completely meaningful), familiarity (0 ¼ very unfamiliar, 100 ¼ very familiar), and semantic closeness (0 ¼ very weakly related, 100 ¼ very strongly related) (Ng and Chan (2007a,b, 2009)). For the Vietnamese participants, the experimenter along with a native Vietnamese interpreter gave instructions to direct the procedures in order to avoid language confusion. The interpreter is a graduate student and has been rated with high Chinese proficiency level based on the Chinese language test conducted by the university language center. In the procedure, there were three major steps in the experiment. The first is an initial comprehension test, followed by the training phase, which consists of recognition and recall training, then a second comprehension test after a 10-min break and a third comprehension test 1 month later. Descriptions are given as follows. In the formal experiment, sixty-five traffic signs were arranged in a random order. Participants first performed the sign comprehension and the sign feature evaluation, as mentioned above. After each sign’s comprehension, the experimenter informed the participant of the correct meaning of the traffic sign, and asked the participant to score the sign on each of the design features. This stage of the experiment lasted for about 60 min, with a 5-min break in the middle. This condition is herein defined as the before training period.

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After finishing the first part of the experiment, training was conducted based on the steps proposed by Ramakrishnan et al. (1999). First, the experimenter explained the correct meanings of all sixty-five traffic signs in their pictorial form, and then started the training, which included recognition and recall. Recognition training: the participants randomly selected traffic signs in their written form, and then tried to match them with their correct pictorial form by examining the meaning on the description cards. When the participants selected the wrong pictorial signs, the experimenter informed them of the meanings of the pictorial signs. Once the participants picked the correct pictorial signs, there was a 3-s pause to allow participants to learn the meaning. After two rounds involving a total of 130 traffic pictorial signs (two rounds with all 65 signs) and once all correct answers were given, recognition training was finished. Recall training: the participants described the correct meanings of the signs from randomly selected pictorial cards. When the meanings were wrong, the experimenter informed them of the correct meanings. The wrong signs were placed into the pool of pictorial cards again until there were two rounds with all answers correct; at this point, training was considered complete. The two forms of training mentioned above lasted for approximately 100 min. After the completion of the two forms of training, there was a 10-min break during which the participants played a poker game to prevent memorization (Wogalter et al., 1997). Immediately after this break, participants’ comprehension of the 65 signs was tested for a second time. At the second part, participants were administered a comprehension test. The experimenter immediately provided the participants with 65 random traffic signs as part of the comprehension test. This test lasted for about 20 min and is herein defined as the condition immediately following training. Comprehension was tested for a third time one month after training. The steps were the same as in the second condition, that is, the comprehension test immediately following training. In addition, the experimenter first ensured that the participants did not learn the traffic signs in the past month, and the signs in this test appeared in a new random order. One concern was whether participants would be reviewing the signs in their daily lives. However, participants recruited for this study all live either in the campus dormitory (especially for all of the Vietnamese) or the surrounding campus suburban area, and most of them commute by bicycles which makes them very unlikely to experience those traffic signs examined in this study, although the authors admit that it’s still somewhat likely a few might have again seen the traffic signs during this one month. In addition, participants were not aware in advance that this study would have another experimental stage after one month. Furthermore, based on the solid statistical analysis results, both groups’ recognition and comprehension scores remained high after one month had passed, indicating that a certain amount of training effect was sustained. 2.5. Data collection and analysis Scoring was done in accordance with ISO 9186 (2001). Three independent scorers carried out scoring. These three scorers were provided with the correct answers for correct meanings. No sign pictures were shown to avoid scoring being affected by the scorer’s subjective biases. The final score equals to the average score of the three independent scorers. As for scoring standards, correct understanding of the meaning of a picture (over 80% understood) earned one point; getting very close to the correct meaning (understood 66e88%) was given 0.75 points; getting close to the correct meaning (understood 50e65%) was given 0.5 points. Giving an answer

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opposite to the correct meaning caused one point to be deducted, and 0 points were awarded for any other answer. If the scorer did not know what score to give for a test subject’s answer, a consensus could be reached through discussion with the other scorers. Analysis of variance of the results was carried out using version 12.0 of the SPSS statistical software package, and then by 2
4
3 ANOVA followed by post hoc analyses using Least Significant Difference (LSD) testing to examine comprehension performance. The LSD test was applied to groups that showed differences in the Analysis of Covariance test in order to find which group created the difference. The Pearson’s Correlation Analysis technique was used to examine the inter-relationship between understanding and sign characteristics. 3. Results 3.1. Comprehension The research consisted of a 2 (countries of origin: Vietnam vs. Taiwan; between-subjects)
4 (types of sign: warning, prohibition, auxiliary, and indicatory; within-subjects)
3 (training conditions: before training, immediately after training, one month after training; within-subjects) mixed-factorial experiment. We tested the hypotheses that training condition, sign types and country of origin affect comprehension, as shown in Table 1. The ANOVA showed that the traffic signs, country of origin, and training condition had statistically significant effects on comprehension [F(1,58) ¼ 76.55, p < 0.001；F(3,174) ¼ 54.67, p < 0.001；F (2,116) ¼ 355.27, p < 0.001, respectively]. Post-hoc analyses revealed that warning signs (0.75), prohibition signs (0.77), and indicatory signs (0.78) were more often comprehended than auxiliary signs (0.64). The average comprehension was 0.52 before training, but increased to 0.94 immediately after training. After one month, the average was 0.75. Overall, the comprehension of the Taiwanese group (0.81) was higher than the Vietnamese group (0.65). The two-way interactions between training condition x country of origin were significantly different in traffic sign comprehension [F(2,116) ¼ 7.862, p < 0.01]. In the Taiwanese group, the average comprehension was 0.63 before training, then 0.98 after training. The Taiwanese group’s performance was significantly higher after one month than before training [F(2,58) ¼ 225.925, p < 0.001]. For the Vietnamese group, the average comprehension was 0.41 before training, and 0.89 after training. The Vietnamese group’s performance was significantly lower before training but both groups showed similar performance immediately after training. After one month, the comprehension of the Vietnamese group was still higher than before training [F(2,58) ¼ 161.575, p < 0.001], as shown in Fig. 1.

Fig. 1. Subjects’ mean comprehension scores by training and country of origin.

The two-way interactions between the traffic signs x training condition was significantly different in traffic sign comprehension [F(6,348) ¼ 5.102, p < 0.01]. The comprehension of the four types of traffic signs prior to training, immediately following training and one month after training, is shown in Fig. 2. Comprehension significantly increased from the period prior to training to the test being administered one month after training. Indicatory signs (0.27) showed the greatest improvement, followed by warning signs (0.26), prohibition signs (0.23), and auxiliary signs (0.16). Auxiliary signs showed a greater comprehension decrease in the month following training than did the other signs.

3.2. Traffic sign features 3.2.1. Descriptive statistics for the Taiwanese group The traffic signs’ features were evaluated on five categories using a 0e100 rating scale. All of the mean ratings exceeded 50 percent for familiarity (53.06), concreteness (66.23), simplicity (72.40), meaningfulness (65.03), and semantic closeness (75.64). Indicatory signs had the lowest concreteness rating (63.28), and

Table 1 Subjects’ mean comprehension at each level of the independent variables. Variable Country of originb Taiwan Vietnam Trainingb Immediately following training One month after training Before training Sign Typeb Warning signs Prohibition signs Indicatory signs Auxiliary sign a b

Mean

Standard Deviations

LSD testa

0.81 0.65

0.22 0.38

A B

0.94 0.75 0.52

0.10 0.17 0.21

A B C

0.75 0.77 0.78 0.64

0.21 0.18 0.21 0.27

A A A B

Values with same letter are not significantly different. Significant at a < 0.01 level.

Fig. 2. Subjects’ mean comprehension scores of four types of traffic signs before training, immediately following training, and one month after training.

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auxiliary signs had the lowest familiarity, simplicity, meaningfulness, and semantic closeness ratings (50.40, 66.88, 60.58, and 69.78, respectively). The Appendix shows which signs had the lowest and highest ratings for familiarity, concreteness, simplicity, meaningfulness, and semantic closeness. The “Lane forbids entry” sign had the lowest familiarity rating (14.33), and the “Keep right” sign had the highest semantic closeness rating (95.33). 3.2.2. Descriptive statistics for the Vietnamese group The traffic sign features were evaluated on five categories using a 0e100 rating scale. The mean familiarity rating (40.76) was below the mid-point rating, showing that the subjects were slightly unfamiliar with Taiwanese traffic signs. Ratings for the other four sign features were as follows: concreteness (59.90), simplicity (64.16), meaningfulness (60.93), and semantic closeness (74.33). Auxiliary signs had the lowest ratings: familiarity (35.17), concreteness (55.33), simplicity (59.14), meaningfulness (56.03), and semantic closeness (70.62). The Appendix shows the signs with the lowest and highest ratings for familiarity, concreteness, simplicity, meaningfulness, and semantic closeness among the Vietnamese. The “Parking forbidden temporarily” sign had the lowest familiarity and semantic closeness ratings (6.70 and 51.13, respectively), and the “Snow chains required” sign had the lowest concreteness, simplicity, and meaningfulness ratings (28.87, 35.07, and 25.30, respectively). Notably, “No parking,” which involves Chinese characters, showed the highest scores for semantic relation (88.87). 3.3. Relationships between traffic sign features and comprehension In this study, the scores of the five sign design features were normally distributed (KolmogoroveSmirnov, P > 0.05). The comprehension score was equal to the average comprehension score of the 3 training stages: before training, immediately after training, and one month after training. The Pearson correlation coefficients for the relationship between traffic sign comprehension and the different sign features are shown in Table 2. For both subject groups, concreteness and meaningfulness were highly correlated with traffic sign comprehension (for the Taiwanese group: r ¼ 0.97, n ¼ 65, p < 0.001; for the Vietnamese group: r ¼ 0.95, n ¼ 65, p < 0.001). Semantic closeness had the highest positive correlation with comprehension (for the Taiwanese group: r ¼ 0.88, n ¼ 65, p < 0.001; for the Vietnamese group: r ¼ 0.80, n ¼ 65, p < 0.001), followed by meaningfulness (for the Taiwanese group: r ¼ 0.88, n ¼ 65, p < 0.001; for the Vietnamese group: r ¼ 0.60, n ¼ 65, p < 0.001), concreteness (for the Taiwanese group: r ¼ 0.86, n ¼ 65, p < 0.001; for the Vietnamese group: r ¼ 0.57,

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n ¼ 65, p < 0.001), familiarity (for the Taiwanese group: r ¼ 0.71, n ¼ 65, p < 0.001; for the Vietnamese group: r ¼ 0.42, n ¼ 65, p < 0.001), and simplicity(for the Vietnamese group: r ¼ 0.27, n ¼ 65, p < 0.05). The feature of simplicity had no significant effect on the Taiwanese’s comprehension of traffic signs, while all five sign features were significantly correlated to comprehension for the Vietnamese group. The “drop” represented the decrease in traffic sign comprehension from immediately after training to one month after training. For both groups, the drop was clearly negatively correlated to comprehension (Taiwanese group: r ¼ 0.92, n ¼ 65, p < 0.001; Vietnamese group: r ¼ 0.89, n ¼ 65, p < 0.0001). In addition, the feature of semantic closeness was more negatively correlated to the drop than the other traffic sign features (Taiwanese group: r ¼ 0.82, n ¼ 65, p < 0.001; Vietnamese group: r ¼ 0.60, n ¼ 65, p < 0.001). 4. Discussion Users from Vietnam and Taiwan differed significantly in their comprehension of traffic signs. Compared to the Vietnamese participants, the Taiwanese participants were more likely to comprehend the traffic signs. The mean of the familiarity rating scores for the Taiwanese (53.06) is higher than for the Vietnamese (40.76) [t(28) ¼ 2.749. p < 0.001]; therefore, this result seems to indicate that the Taiwanese are more familiar with these signs, and familiarity will improve comprehension (Ben-Bassat and Shinar, 2006; Rosson, 2002). In different cultures, traffic sign designs are also different. In Vietnam, for example, the background color of warning signs and auxiliary signs is yellow. Furthermore, many signs in Taiwan do not exist in Vietnam (e.g., chained tires). Previous studies have suggested that the subject’s cultural background is a critical factor in sign recognition; thus, the design of signs should take into account cross-cultural influences on sign comprehension (Del Galdo, 1990; Ossner, 1990; Russo and Boor, 1993; Goonetilleke et al., 2001). Taking into account crosscultural influences could reduce the bias caused by cultural differences and enhance the comprehension of signs. This study found that training can significantly enhance sign comprehension, a conclusion supported by previous studies (Ulrich, 1998; Ramakrishnan et al., 1999; Wogalter et al., 1997; Green and Pew, 1978). In addition, there was significant interaction between training and comprehension of traffic signs in both groups. The results indicate that after training, the two groups’ comprehension was significantly enhanced (the Taiwanese: 0.20; the Vietnamese: 0.25). Immediately after training, the participants’ comprehension was significantly strengthened. Although the comprehension drops after one month, it remains better than that

Table 2 Correlations between traffic sign features and comprehension. Familiarity Concreteness Simplicity Meaningfulness Semantic Closeness Comprehension Drop a b

Taiwanese Vietnamese Taiwanese Vietnamese Taiwanese Vietnamese Taiwanese Vietnamese Taiwanese Vietnamese Taiwanese Vietnamese

0.80b 0.83b 0.26a 0.62b 0.85b 0.86b 0.70b 0.71b 0.71b 0.42b 0.57b 0.19

Correlation is significant at the 0.05 level (2-tailed). Correlation is significant at the 0.001 level (2-tailed).

Concreteness

Simplicity

Meaningfulness

Semantic Closeness

Comprehension

1 0.11 0.45b 0.97b 0.95b 0.85b 0.81b 0.86b 0.57b 0.72b 0.40b

1 0.01 0.52b 0.05 0.43b 0.05 0.27a 0.05 0.06

1 0.87b 0.84b 0.88b 0.60b 0.74b 0.41b

1 0.88b 0.80b 0.82b 0.60b

1 0.92b 0.89b

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before training. This indicates that training can enhance pictorial sign comprehension to a very significant extent (Wogalter et al., 1997; Wang and Chi, 2003). This study found no significant differences in the comprehension of warning, prohibition, and indication signs between the period immediately after training and one month after training. Previous studies found that the results of training indeed are able to increase the comprehension of users. Since both of the comprehension and the 5 design features score of auxiliary signs were the worst as compared to the other 3 types of signs, it is therefore suggested that the auxiliary signs should be redesigned. Before training, the comprehension of all four types of traffic signs fell below the ISO 3846 (1984) 67% guideline for comprehension; however, after training, only auxiliary signs did not meet the ISO 67% guideline. Public information symbols must exceed the 67% recognition rate suggested by ISO 3846 (1984) in order to be recognized as proper signs and standard public information symbols. Therefore, the design features of auxiliary signs are too poor for the two groups to comprehend them to a large extent. This shows that users’ comprehension of signs depends on proper design features and that users will better identify a sign that precisely communicates the semantic meaning (Young and Wogalter, 1990). In contrast, when the sign’s design is unsatisfactory, training can enhance sign comprehension. After training, the comprehension of auxiliary signs increased by 0.16. Thus, training or redesign of auxiliary signs is suggested. The differences in comprehension between the two different groups may be due to the familiarity (or unfamiliarity) with the signs (Ng and Chan, 2007a). With regard to the “Parking forbidden temporarily” sign ( ), the Vietnamese show only a 6.7 average on familiarity, and a 51.13 average on semantic closeness. The reason is because the background color of traffic signs in Taiwan is different from that in Vietnam. As to concreteness, simplicity, and meaning, the sign “Snow Chains Required” received the lowest score in the evaluation. Since the sign does not exist in Vietnam, the Vietnamese cannot recognize it, which indicates that these rare signs are difficult to comprehend (Shinar et al., 2003). Noticeably, the sign “No Parking”( ), which involves Chinese characters, had the highest semantic relation scores (88.87). The Vietnamese students recruited for this study had learned the Chinese language for at least six months and thus the Chinese character 停(“Stop”) in the sign enhanced their comprehension of the sign. Moreover, the design of this sign involves the concept of redundancy. By including the character “Stop” in the prohibitory sign ( ), the participants could comprehend “No parking” using a semantic connection. Signs designed with both descriptions and pictures enhance user recognition ability (Wiseman et al., 1985) and user comprehension (Wolff and Wogalter, 1998). This study found that the five sign features are not equally important: the correlation between semantic closeness and comprehension is the most significant, a conclusion also reached by McDougall et al. (2001). For different cultural groups, semantic closeness is the most important feature, followed by meaningfulness, concreteness, familiarity, and simplicity. In addition, the closer the semantic meaning of the sign, the higher the comprehension and the less the decline of sign comprehension even after a one-month time period (Wang and Chi, 2003). In general, there was a trend where higher scores for the five sign design features implied not only higher sign comprehension but also lower forgetfulness. 5. Conclusion This study examined the effects of sign design features and training on the comprehension of four types of Taiwanese traffic

signs in Taiwanese and Vietnamese users. Comprehension of the different types of traffic signs varied significantly. Users with different cultural/language backgrounds showed significantly different levels of traffic sign comprehension. Training was found to be significantly positive in improving the comprehension of signs in different user groups and, although comprehension decreases after one month, it is still better than comprehension prior to training. For the four types of traffic signs, overall it was observed that none of them reached the ISO 3864 comprehension criterion of 67% prior to training, whereas on the post-training test conducted after one month, only the auxiliary signs fell short of that mark, implying, to some degree, that auxiliary signs should be redesigned cautiously and rigorously. Comparing the five design features in terms of positive correlation to comprehension, semantic closeness was the best predictor, followed by meaningfulness, concreteness, familiarity, and simplicity. The findings of this study provide useful information for improving traffic sign designs so as to increase safety on the road and may serve as a valuable guide for interface designers in designing and evaluating pictorial signs for various types of user and consumer products. This study did not discuss response time and recognition because the participants were required to response correctly as soon as possible (i.e., instantly). For future research, the study of response time to traffic signs is strongly suggested because of the alarming number of traffic accident caused by slower recognition.

Acknowledgment The authors would like to thank the National Yunlin University of Science and Technology for providing volunteer Vietnamese and Taiwanese students in making this study successfully.

Appendix. Supplementary material Supplementary data associated with this article can be found in the online version, at doi:10.1016/j.ergon.2011.08.009.

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