The island traffic signal (ITS) is used to control the flow of traffic through each conventional toll plaza lane, including manual, automatic and dedicated lanes. The user is expected to react to the current state of the signal in the same manner as ramp metering, stopping at the toll collection point and exiting the lane when the signal state changes. Each ITS includes a minimum of two vertically aligned signal heads. Red and green signal heads are typically used in manual and automatic lanes and green and yellow in dedicated ETC lanes. In lanes that provide an electronic toll collection (ETC) capability, the familiar yellow signal head is sometimes added to the ITS to provide ETC user feedback on the status of their account, specifically an account balance that requires payment or replenishment. Another common feature of the ITS is the mounting of an alarm and flashing light to the top of the ITS assembly, both of which are activated when a violation occurs. For plaza lanes installed with violation enforcement equipment, this feature is either not installed or not used.
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