The invention discloses a completely unblocked combined structure consisting of the eight single bridges of a left-side-driving crossroads, and belongs to a combined structure which can realize completely unblocked going-straight and turning-right by using the eight independent uncrossed single-layer arch bridges of the crossroads. The completely unblocked combined structure comprises four single bridges used for going-straight and four single bridges used for turning-right; a middle section of an arch-bend going-straight single bridge is a left protruding arch-bend section which protrudes left; a middle section of a large arch-bend turning-right single bridge is a large arch-bend turning-right section which protrudes left at first and then protrudes towards the opposite side; an arch-bend going-straight single bridge forms a combined single bridge on the outer side of the arch-bend of the large arch-bend turning-right single bridge, so that four single bridges are formed; according to the sequence of clockwise direction, the combined single bridges at a front position are on the outer side of the combined single bridges at a rear position. The completely unblocked combined structure has the advantage that: completely unblocked going-straight and turning-right without cross road occupation is realized by using the four going-straight single bridges and the four turning-right single bridges. Compared with the conventional two-layer or three-layer overpasses of the crossroads, the bridge building cost is reduced greatly and the overpass height is reduced.