A delivery company uses self-driving vehicles to expedite its parcels. To plan a delivery route, the dispatch-centre operator displays special electronic signs before each intersection (in the direction of travel on the right) which determine the vehicle’s direction of movement. If a sign other than one of those in the example appears on the map or it is not possible to go in the specified direction, the vehicle will stop and service is required.
This red line shows the vehicle’s route from its starting point. From the start, the vehicle crossed Green Street, Dotted Street, Grey Street, Yellow Street, and Blue Street.
Which sign should be displayed at the next intersection so that the vehicle continues to Forest Road?