We used a fully interactive PC-based STISIM driving simulator to compare dual-phase Changeable Message Signs (CMSs) and static CMSs. The participants were 120 licensed drivers from three age groups: 18-24, 32-47, and 55-65 years of age. They drove eleven miles on a simulated six-lane highway towards an airport, knowing which airline to look for. Airline information was provided on two separate CMSs located 500 ft (152.4 m) apart on the highway in one condition, or on a single dual-phase CMS in the other condition. The participants took the correct exit on 89.6% of the drives (215 of 240). There were no statistically significant differences between the number of participants who failed to take the correct exit in the dual-phase and the static CMS conditions. On the approach to the CMSs displaying airline information, there were significant differences in average speed between the three age groups--younger drivers drove faster than middle age and older drivers. However, average speeds were not different in the dual-phase and static CMS conditions. Some individuals reduced speed on approaching the CMSs--suggesting similar reductions could occur in real world driving in free flow conditions. There were no differences in the number or magnitude of the speed reductions for the dual-phase and static CMS conditions. In this experiment, displaying airline information on a single dual-phase CMS was as effective in influencing driving behavior as displaying the same airline information on two static CMSs.