Splitter islands

Another effective cross-section treatment to reduce approach speeds is to use longer splitter islands on the approaches (10). Splitter islands should generally be extended upstream of the yield bar to the point at which entering drivers are expected to begin decelerating comfortably. A minimum length of 60 m (200 ft) is recommended (10). Exhibit 6-48 provides a diagram of such a splitter island design. The length of the splitter island may differ depending upon the approach speed. The AASHTO recommendations for required braking distance with an alert driver should be applied to determine the ideal splitter island length for rural roundabout approaches.

A further speed-reduction technique is the use of landscaping on the extended splitter island and roadside to create a “tunnel” effect. If such a technique is used, the stopping and intersection sight distance requirements (sections 6.3.9 and 6.3.10) will dictate the maximum extent of such landscaping.