Alicia A Williams

Driver Understanding of Sequential Portable Changeable Message Signs in Work Zones

Results of a Texas Transportation Institute driving simulator study are presented. The studys focus was the ability of motorists to capture and process information on two portable changeable message signs (PCMS) used in sequence (i.e., one PCMS following another along the edge of the roadway such that each PCMS contains part of a single message). The purpose of the PCMS is to convey information about upcoming traffic situations. Results indicate the need to keep messages at or below the four-unit maximum recommended in existing guidelines. It was found that presenting five units of information on sequential PCMS resulted in low comprehension rates, below what would be acceptable for highway applications. However, by keeping the message length to four units, it appears that the use of the sequential PCMS will result in comprehension rates comparable with those obtained by presenting the same information at a single location on a large dynamic message sign. Comprehension may be enhanced by repeating one line of the message on both PCMS used in a given sequence.