Tall buildings, high rise buildings, skycrapers and tall structures such as, for example, Unicredit Tower in Milan, Italy (231m) or Burj Al Arab in Dubai, U.A.E. (322m) are hazardous to aviation safety because of their height and location and should be marked with obstruction lights according to international regulations.
|H < 45m||1 level of low intensity obstruction lights shall be used|
|45m < H < 105m||2 levels of obstruction lights shall be used: top level with medium intesity, intermediate with low intensity|
|105m < H < 210m||4 levels shall be used: top with medium intesity, 1stintermediate with low intensity, 2nd intermediate with medium intensity, lower level with low intensity|
|L and W < 45m||4 obstruction lights shall be used (one per corner)|
|45m < W < 90m||1 additional obstruction light shall used in the middle of width W|
|L and W > 90m||obstruction lights shall be spaced at longitudinal interval not exceeding 45m|