Dynamic merge control, or junction control, automatically manages the entry of vehicles into merge areas. Agencies can change the amount of access based on traffic demand by using light-up signs to open or close an extra lane at an exit or entrance ramp. On a two-lane entrance ramp where the left lane of the ramp merges with the outside lane of the freeway, either the outside freeway lane or the left lane of the entrance ramp would be closed prior to the merge (depending on traffic volume).