If the OBU in the Prepaid Toll mode is signalling a low balance of Prepaid Toll, increase the Prepaid Toll amount without delay at the nearest Customer Point. The OBU 1374 signals a low Prepaid Toll balance by the first button flashing green along with an acoustic signal. The OBU Sitraffic Sensus Unit and Billien OBU indicate a low Prepaid Toll balance by the flashing € symbol (Billien OBU 5051: the € symbol is lit up yellow) together with the flashing position LED indicator and an acoustic signal at the same time. When the Prepaid Toll balance reaches €0, the OBU will be blocked.
Similarly, in the Postpaid Toll mode the first button on the OBU 1374, and on the OBU Sitraffic Sensus Unit and Billien OBU the € symbol (Billien OBU 5051: the € symbol is lit up yellow) combined with the flashing position LED indicator, flashes if the total amount travelled gets close to the amount of the bank guarantee or cash deposit. This warning informs the operator/vehicle driver that the amount of the bank guarantee or cash deposit should be increased.
If failing to pay the Toll and/or other liabilities even within 3 calendar days from the due date, the System Operator is entitled to block all the On-Board Units of the Vehicle Operator being in delay with the payment of Toll and other liabilities; every blocked On-Board Unit indicates the blocked status to the Vehicle Operator and/or Driver.
If a vehicle transporting an OBU that is not to be used during the journey to record toll transactions is driving on specified sections, the vehicle operator to which the OBU is assigned is required to ensure proper transportation of the OBU in accordance with the instructions of the system operator.