This paper has presented some of the problems inherent in the evaluation of traffic signs and has summarized a number of laboratory methods used for such evaluation. Although they have definite limitations, intuitive methods (especially the determination of population stereotypes and input from experts in the traffic engineering profession) are valuable in the early stages of the development of new symbols. These techniques provide the raw material or candidate symbols for objective evaluation using a variety of methods. Paper-and-pencil techniques provide an easy and inexpensive approach to establishing the comprehension, or meaning, of symbols (the most important single criterion of effectiveness). Legibility distance would likely be the next most important criterion in evaluating a traffic sign, with speed of comprehension (reaction time) and glance legibility less critical. However, it should be noted that reaction time has been shown to be highly correlated with legibility distance on the roadway. Note that the criteria of legibility distance, reaction time and glance legibility apply to word signs as well as to symbols, while comprehension and preference measures are more appropriate for evaluation of symbolic messages. The preference measures are generally of less value, since the judgements made are done so on the basis of individual impressions rather than objective information. The greatest need at the present time is to validate the various methods available, and to determine the most effective combination of techniques to be used for traffic sign evaluation. Transportation authorities would be well advised to put more time and effort into establishing the validity of the various techniques available for the evaluation of traffic signs, and in particular to determine the relative importance of each method and the optimal combination of methods to be used. Such an undertaking must involve a multidisciplinary approach. Traffic engineers can provide a wealth of practical experience relevant to the problems with existing signs and the probable effectiveness of new signs. Graphics artists can provide expertise on the detailed design and format of traffic sign messages. The psychologist's contribution comes from his/her knowledge of driver information processing abilities and familiarity with technologies appropriate to the measurement of traffic sign perception. It is clear that no one of these disciplines has the expertise or mandate to solve this important and complex problem by itself. (A)
Samenvatting