ISO/FDIS 9186 Procedures for the development and testing of graphical symbols

Terminology

Referent - idea or object that the graphical symbol is intended to represent

Variant - alternative design for a given referent

ISO/FDIS 9186 Standard

The international standard ISO 9186:2001 [ISO 9186] defines procedures for testing the comprehensibility of graphical symbols. The procedures describe two testing methods, the comprehensibility judgement test and the comprehension test. Each test is intended to determine the most comprehensible variants of a graphical symbol. The standard defines rules for the selection of respondents in a representative way, as well as rules for selecting the most comprehensible graphical symbol variant for each referent.

Comprehensibility judgement test

The method for selecting the most comprehensible variants out of big range of graphical symbols.

Different graphical symbol variants for each referent are presented together with their intended meaning in a standardized way. The respondents' task is to judge the comprehensibility of each variant, giving the percentage of people in their country, who they would expect to interpret the symbol correctly. The standard defines different thresholds for the mean and median values of the judgements given by the respondents. According to these boundaries, one can decide, whether a variant can be accepted or at least subjected to the comprehension test. If no variants exceed any of the thresholds, new variants should be collected.

Comprehension test

The method for evaluating how well the graphical symbol communicates its intended message.

Variants of graphical symbols are presented to the respondents in random order. The respondents have to write down what they think a symbol means. In a second step the answers are classified by 3 independently working judges into several categories, ranging from "Correct understanding of the symbol is certain" to "No response is given". The standard defines how to calculate a score for each variant. Similar to the comprehensibility judgement test, there are threshold values given, to determine which variants may be accepted as a standardized graphical symbol.

Example Project: Evaluation of Pictograms/Symbols for the trans-european road network

Due to the complexity of road information in the Trans-European road network, there is a strong need to present information to the driver in a standardized and comprehensible way. Graphical symbols intended to be displayed on variable message signs have been evaluated applying the ISO 9186 standard.

K.Siebenhandl and H.Risku describe that in the comprehensibility judgement test [Siebenhandl and Risku, 2007a] a total of 243 variants were tested during the comprehensibility judgement test for 33 referents. 825 voluntary drivers from Austria, Hungary, Spain, and the Czech Republic participated in the test as respondents. 28 variants reached the threshold for immediate acceptance, 56 were proposed for a redesign. The results provided the pre-selection for next testing phase - comprehension test.

The comprehension test was carried out in Austria, Hungary, and the Czech Republic [Siebenhandl and Risku, 2007b]. A total of 84 variants for the 33 referents were tested on 604 respondents. The test resulted in the recommendation of pictorial symbols for 20 of the referents. The test indicated that more symbolic pictograms (like "City Center" or "Obstacles on the Road") are less likely to be comprehended, than sign containing elemental objects like ("Ferry Boat", or "Deer on Road"). In the report [Siebenhandl and Risku, 2007b] it is recommended, that the symbols with a low ISO score should be advertised to be learned, before displaying them. The results provided the pre-selection for next testing phase comprehension test in impaired visibility conditions.

Conclusions

Only after succusfully passing the Comprehension Tests, the pictograms may be regarded as understandable and worth of employment on the Trans-European Road Network.

[Siebenhandl and Risku, 2007a][Siebenhandl and Risku, 2007b]

The example project shows that the comprehensibility of the graphical symbols need to be evaluated in order to know how comprehensive those are, even if designed by professionals. Small changes in design may cause clear differences in the understanding which the designers might not have anticipated and there are also cultural differences. Also the feedback from evaluation can provide the designers valuable input to re-design the graphical symbols, so at its best the test methods are used in close co-operation with designers to allow iterative development of graphical symbols – and improved comprehensibility.

References

[ISO 9186] ISO/FDIS 9186:2001: International Organization for Standardization, http://www.iso.org/iso/catalogue_detail?csnumber=23669

[Siebenhandl and Risku, 2007a] Siebenhandl, Karin; Risku, Hanna; Brugger, Christof & Simlinger, Peter: Evaluating the Comprehensibility of Visualized Information for the Trans-European Road Network (TERN). In: Proceedings of the 20th Enhanced Safety of Vehicles Conference, June 18-21, 2007, Lyon, France.

[Siebenhandl and Risku, 2007b] Siebenhandl, Karin; Risku, Hanna; Brugger, Christof & Simlinger, Peter: Evaluating the comprehensibility of visualized information for the Trans-European Road Network (TERN) as part of the EU Project IN-SAFETY: INfrastructure and SAFETY. In: Proceedings of the International Conference Road Safety and Simulation 2007, November 7-9, 2007, Rome, Italy.