Переход от активного залога к пассивному: 1)the workes had constructed the first metro line by may 1935. 2) the first line connected two districts. 3) moscow metro builders did the construction work in difficult geological conditions. 4) during the great patriotic war the metro builders continued the work. 5) the belt line links 18 districts of the capital. 6) an automatic driver conducts trains according to the schedule. 7) before holidays muscovites decorate the streets of the city with flags, portraits, flowers and garlands of coloured bulbs. 8)an automatic driver has undergone successful tests.

Не спец в английском. Я бы так выполнил это задание.

1) The first metro line had been constructed (by workers) by May 1935
2) Two districts were connected with the first line
3) The construction work was done (by Moscow metro builders)  in difficult geological conditions
4) The work was continued During the Great Patriotic War
5) 18 districts of the capital are linked with the belt line
6) Trains are conducted with an automatic driver according to the schedule
7) The streets of the city are decorated  with flags, portraits, flowers and garlands of coloured bulbs before holidays 
8) An automatic driver was successfully tested

(В последнем предложении не буквальный переход, а по смыслу. "has undergone"  - само по себе с пассивным значением, хотя формально это активный залог. Это ощущается и в русском языке: автопилот(автомашинист) подвергся успешно испытаниям успешно испытания). Поэтому формальное обращение будет выглядеть странно: Successful tests have been undergone with an automatic driver)