Traffic signs are ubiquitous in the road environment, and are a crucial and cost-effective means of ensuring traffic safety. In Queensland, Australia, a class of temporary traffic signs is used for roadworks applications, and has recently been expanded to include Multiple- Message Signs; a novel, and as yet empirically untested system, which presents numerous advantages in terms of flexibility and economy. However, potential Human Factors problems surround aspects of the design of multiple message signs. In particular, the efficiency with which information is communicated may be compromised relative to single message signs.
This project involved a series of laboratory studies focusing on the behavioural requirements of temporary roadworks signs, beginning with the improvement of response characteristics of a sign used to communicate lane-closure. In the first empirical study, a proposed redesign of the Lane-Status sign based on principles of warning communication was found to be more effective than the original sign.
The same sign was then examined in the context of multiple-message presentation, and significant costs with respect to the speed and accuracy of responses relative to single message presentation were found. A subsequent study investigated multiple-message presentation of speed limit information, which is more familiar and widely encountered than lane-closure information. Similar costs for multiple-message presentation were found. However, there were data to suggest that the additional information in multiple-message signs, if used correctly, may offer drivers an additional incentive to reduce speed.
The next two studies were concerned with the effects of presentation, content type (e.g., speed-limit, symbolic and text-based) and visual clutter on recognition and visual search for traffic signs. The presentation of information via multiple message signs was compared with spatially distributed single message signs, with information matched with respect to message length and sign content. Overall advantages for multiple-message presentation were found for recognition, which were particularly robust for speed limit information. The results for visual search indicated some benefits to multiple message presentation, but were less decisive than those for recognition.
The final two studies investigated the possibility of improving response characteristics of single-message signs with sequential, rather than individual presentation. The role of the temporal interval between successive sign presentations was explored, which has implications for the feasibility of sequential presentation in practice. In addition, the nature of sign pairs presented in sequence - identical, or of the same meaning – was found to be important. Generally, benefits to sequential presentation diminished with increases in the temporal separation interval.
In terms of practical implications, the viability of introducing the proposed design changes to the Lane Status sign is discussed. The results pertaining to multiple-message signs are evaluated in the context of published design guidelines, and theoretical and practical issues surrounding sequential sign presentation are reviewed. Finally, possibilities for future research, in part based on the limitations of the current work, are expounded.