1. When a vessel is navigating by radar, there shall be at all times in the wheelhouse a person holding a certificate required by the competent authorities for that section of the inland waterway and for the type of vessel he navigates and the certificate referred to in article 4.06, paragraph 1 (b), and a second person sufficiently conversant with this method of navigation. However if the wheelhouse is designed for radar navigation by one person, it is sufficient that the second person can, if necessary, be summoned to the wheelhouse immediately.
2. As soon as a vessel proceeding upstream observes oncoming vessels on the radar screen, or when it is approaching a sector where there might be vessels not yet visible on the screen, it shall communicate by radiotelephone to the oncoming vessels its category (for example, pushed convoy, high-speed vessel), name, direction and position, and agree with these vessels on a procedure for passing.
3. As soon as a vessel proceeding downstream observes on the radar screen a vessel whose position or course may cause a dangerous situation and which has not established contact by radiotelephone, the vessel proceeding downstream shall draw the attention of this vessel to the dangerous situation by radiotelephone and agree on a procedure for passing.
4. When radiotelephone contact cannot be established with the oncoming vessels, the vessel proceeding downstream shall:
(b) Reduce speed and, if necessary, stop.
A vessel proceeding upstream shall, as soon as it hears the signals referred to in paragraph 4 (a) above or observes on the screen vessels whose position or movements might cause a dangerous situation, or when it is approaching a section where there might be vessels not yet visible on the screen:
(c) Give one long blast and repeat this signal as often as necessary;
(d) Reduce speed and, if necessary, stop.
5. Any vessel navigating by radar and called by radiotelephone shall reply by radiotelephone, giving its category (for example, pushed convoy, high-speed vessel), name, direction and position. It shall then agree on a passing procedure with the oncoming vessel; a small craft, however, shall only indicate on which side it is giving way.