Evaluation of Signs and Markings for Partial Continuous Flow Intersection

The continuous flow intersection (CFI) supports high traffic flow where there is a large volume of left turns. The CFI accomplishes this by moving left-turning traffic to the left side of a highway before the main intersection. Left turns can then be made at the same time as the opposing through movement. This eliminates the need for separate left turn signal phasing and reduces the potential conflict points between left-turning and through traffic. Because CFI left turn movements begin well in advance of the road junction, signing and marking requirements are different from those for conventional intersections. This study reports the results of a driving simulator study that compared alternative signing and marking options. Three strategies for navigation signing in advance of the crossover were evaluated: overhead signing and two different ground-mounted sign alternatives. In addition, on a leg of the CFI that did not cross left-turning traffic to the left side of the roadway, alternative schemes for emphasizing the location of the stop line were evaluated. The results showed that the ground-mounted navigation signing treatment that included a Keep Left advance sign was as effective as an overhead navigation sign. All treatments for designating the stop line were equally effective.