Successful communication of traffic information to motorists. via intelligent transportation systems (ITS) is critical for improved safety and traffic flow in high risk areas such as work zones. The conveyance of pertinent, real-time information through variable message signs (VMS) technology is integral to ITS. The content of messages presented on VMS is especially important given that drivers must detect, comprehend, and translate signage information while being occupied to some degree with the task of driving their vehicle. A simulation experiment was conducted, using a prototype dual-task methodology developed to examine message content of VMS in work zones and to assess the effect of message type, display type, sign content, and repeated exposure to the signs on message comprehension and translation. Twenty participants (mean age = 25 yrs) viewed a computer simulation of a section of road leading to a work zone site that had VMS along the road side. Signs were of two message types (speed vs. time signs), three display types (two inexpensive; one with full text wrap-around and one with partial wrap-around; and one expensive matrix of three lines by eight characters flashed twice), two similar message versions. and a complete repeat for reliability in a 2 x 3 x 2 x 2 repeated measures design. The primary task required attending to a grid line in the rearview mirror and remembering which signal had appeared. The concurrent, secondary task was reading the message content of VMS that were optically expanding at a rate comparable to traveling at 111 kilometers/hour (70 mph). Questions regarding the grid line signal and sign comprehension and interpretation followed. The results support this methodology's capacity to evaluate message content of VMS, especially in an ITS context. Message type significantly affected comprehension of sign content and translation of the consequences of the information conveyed, but display type did not influence responses to time or speed signs. This suggests a potential for substantial savings from the increased use of inexpensive displays instead of full-matrix units. Future research should involve assessment of the validity of the computer simulation, in addition to testing behavioral responses to message content either with a follow-up on-road and/or driving simulation study.
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