AN EVALUATION OF FLUSH MEDIANS AND TWO-WAY, LEFT-TURN LANES ON FOUR-LANE RURAL HIGHWAYS. INTERIM REPORT

Three types of medians are typically used on four-lane rural highways in Texas: raised (or depressed) medians; two-way, left-turn lanes (TWLTLs); and flush medians. With flush medians, the area between the travel lanes is paved and can easily be traversed by a vehicle. This type of median is typically used in areas that transition from rural to suburban. The purpose of this research was to examine the differences in the operations and safety of four-lane rural highways with TWLTLs and four-lane rural highways with flush medians. A review of accident rates found that there were no statistical differences in accident rates of highways with TWLTLs and highways with flush medians when driveway densities were low. Field studies also showed that there was no difference in the way they should use flush medians and TWLTLs. Texas state law states, however, that it is illegal for motorists to use flush medians as a storage and acceleration/deceleration area for turning left into and out of adjacent properties. The results of this research suggest that drivers ignore the meaning of the solid yellow lines used to mark flush medians. Therefore, in order to promote uniformity and consistency, it is recommended that flush medians be used only on highways where the frequency and spacing of driveways permit individual median openings at each driveway. In cases where this is not possible, it is recommended that TWLTLs be used on four-lane rural highways.