ICAO - Lighting of objects with a height less than 45 m above ground level

Recommendation.— Low-intensity obstacle lights, Type A or B, should be used where the object is a less
extensive one and its height above the surrounding ground is less than 45 m.

Recommendation.— Where the use of low-intensity obstacle lights, Type A or B, would be inadequate or an
early special warning is required, then medium- or high-intensity obstacle lights should be used.

Recommendation.— Low-intensity obstacle lights, Type B, should be used either alone or in combination
with medium-intensity obstacle lights, Type B.

Recommendation.— Medium-intensity obstacle lights, Type A, B or C, should be used where the object is an
extensive one. Medium-intensity obstacle lights, Types A and C, should be used alone, whereas medium-intensity obstacle lights, Type B, should be used either alone or in combination with low-intensity obstacle 

lights, Type B.

Note.— A group of buildings is regarded as an extensive object.