The Directorate-General of Public Works and Water management of Utrecht has plans to change the normal pattern of one car per green light phase at a ramp meter to two cars per green light phase. With this measure traffic jams at the underlying road-network could possibly be avoided. Because the measure deviates from the common measure nationally implemented and deviates from the expectation patterns of the road user, it is important that the new measure is communicated sound and clear. TNO-HF has developed a traffic sign, including a pictogram and text message for this purpose. The development of the traffic sign is realised in four phases. By means of an informative discussion with the Directorate-General of Public Works and Water management of Utrecht the requirements of the sign were determined. This discussion was followed by a brainstorm session and an internal workshop were five pictograms and three text messages to support the pictograms, were developed. Special attention has been given to understandability, safety, understandability, legibility, use of colour and visibility under various weather and traffic conditions while keeping in mind the relevant rules and standards. In a comprehensibility study fifty road-users were interviewed. First of all we determined whether the respondents noticed the traffic sign in a set of photos from a ramp meter. In addition questions were asked in respect to one of the five traffic signs in terms of interpretation of the sign and effects on driving behaviour. Subsequently we presented the general meaning of the sign and showed all five pictograms asking the respondents to rankorder the pictograms in terms of comprehensibility. We asked the same questions for the text messages. Via analysis of the results of the questions in the interview it was determined which combination of pictogram and text messages should be used to convey the information best. We found that in relation to the pictograms few erroneous interpretations of the signs were given, in spite of the fact that the information on the sign was unusual and the sign itself was unknown. Most respondents offered the interpretation that two cars were allowed to pass during the green light phase of the ramp meter. The text messages spoke for themselves naturally. The rankordering of the pictograms did not show a clear pattern. However a distinct disapproval was found in relation to a group of signs: the warning sign was not considered apparent. The rankordering of the text messages showed a clear pattern. Based on the subsequent answers of the respondents to the questions an advice has been issued for a traffic sign. Based on the results of the experiment we have proposed a few adjustments to optimise the comprehensibility of the resulting pictogram and text of the traffic sign. (Author/publisher)
Abstract