Blue sign

A blue sign or blue board is used by inland waterways vessels within the Trans-European Inland Waterway network when performing a special manoeuvre or passing on the starboard side.

On navigable waterways vessels normally pass each other on the port-side, so the display of the blue sign and flashing white light signal intention to pass each other on the starboard-side.

[2][3][4][5] The Code Européen des Voies de la Navigation Intérieure (CEVNI) regulations require upstream vessels operating on the opposite side to display a light-blue sign and scintillating (flashing) white light.

[7] The presence and status of the blue sign is transmitted by the ship's Inland-Automatic Identification System (Inland-AIS) transponder to other vessels.

The status of the sign is transmitted using two bits of the "regional application flags"/"special manoeuvre field" in the AIS position reports.

Rotating-style blue sign laying flat when not active. There is a 5 cm white border and the light is in the centre