A Simulator Study of Driver Response to Changeable Message Signs of Differing Length and Format

Highway congestion nationwide continues to increase, and three Florida urban areas rank among the top ten. Florida has been studying and implementing intelligent transportation system technologies to address its congestion problems, with a focus on its special populations such as the elderly and multi-cultural groups for which English is not the primary language. One of these technologies most widely deployed is the changeable message sign (CMS). Fifty-two CMSs are operational in Florida, with 39 more scheduled for deployment soon. Although CMSs have the potential to facilitate travel, certain issues must be considered to ensure that they do not exacerbate the congestion problem. One key CMS operational issue is the number of phases required to present a complete message. "On-time" for two-phase messages varies from 2.5 to 5 seconds per phase across the State. Of course, the appropriateness of this on-time depends not only on the characteristics of the CMS itself, but on the road, traffic and weather conditions, and driver characteristics. This study, funded by the National Institute on Aging, investigated issues related to the number of CMS phases and their on-time. The authors used a low-cost, interactive driving simulator supplemented with a video monitor above the main display. While simulator screens presented interactive road and traffic conditions, the supplemental monitor displayed the CMS. Young and old drivers drove the simulator under different workload conditions and responded to road closure/detour information on the CMS. All CMS displays were developed in accordance with accepted guidelines and were reviewed for content by independent experts. Results showed consistent and significant age effects across all tested conditions. In addition, the authors found significantly poorer response for all drivers under the two-phase CMS, despite the fact that the message "on-time" was nearly 2 seconds longer than that used in two major Florida jurisdictions. The findings have implications for CMS design and operation in Florida and in other jurisdictions with similar populations.