To be compliant with the Belgian Road Pricing regulations, your OBU must always be switched on when you drive on the Belgian roads, which means that your OBU should normally already be switched on when you approach the Liefkenshoek Tunnel.

However, should this not be the case, your OBU will (if it is in sleep mode and has enough battery or if it is connected via the power cable) automatically wake up when your truck is approximately two metres away from the gantries of the tunnel and it will start calculating the toll.