Effectiveness of Using Diagonal Yellow Arrows on Lane-Use Control Signals

Lane-use control signals (LUCSs) are important elements of a traffic management strategy for mitigating congestion and enhancing safety, especially during peak travel times. The Manual on Uniform Traffic Control Devices (MUTCD) allows the use of a downward green arrow indication as well as a yellow X-indication and a red X-indication. In 2014, the Virginia Department of Transportation requested and obtained FHWA approval for an experiment to evaluate the diagonal downward yellow arrow indication. Previous studies had shown that this indication had several benefits relative to the yellow X-indication. A stated preference survey was conducted to evaluate driver understanding of LUCSs on I-66 and on I-95 express lanes. Survey results indicated that more than six times as many participants preferred the diagonal downward yellow arrow indication to the yellow X-indication, regardless of driver age or travel frequency on the test corridors. Traffic operations center staff anecdotally observed several positive changes in driver behavior while the diagonal downward yellow arrow indication was in use. Preliminary operational and safety results were reviewed after deployment of the diagonal downward yellow arrow indication. Results indicated that driver understanding of the diagonal downward yellow arrow indication was superior to that of the MUTCD-approved yellow X-indication, and no negative effects on safety or operations were observed. The diagonal downward yellow arrow indication appears to be a useful new LUCS indication and could improve traffic management.