Complex sentence: Seventy-nine trains out of a fleet of 86 are needed to run the line's peak service, and one unit (166-566-366) was severely damaged by the terrorist attack of 7 July 2005.
Split into simpler sentences: Seventy-nine trains out of a fleet of 86 are needed to run the line's peak service. One unit (166-566-366) was severely damaged by the terrorist attack of 7 July 2005.