3-2-2. WARNING SIGNAL
Direct a general warning signal, alternating red and green, to aircraft or vehicle operators, as appropriate, when:
NOTE: The warning signal is not a prohibitive signal and can be followed by any other light signal, as circumstances permit.
- Aircraft are converging and a collision hazard exists.
- Mechanical trouble exists of which the pilot might not be aware.
- Other hazardous conditions are present which call for intensified pilot or operator alertness. These conditions may include obstructions, soft field, ice on the runway, etc.