Composite bridge or composite tunnel for left-hand traffic comprising four y-shaped units

A composite bridge or composite tunnel for left-hand traffic is composed of four independent Y-shaped arch bridges or tunnels, wherein each bifurcated arch bridge comprises a straight going arch bridge (2) and a right-turn bridge (3) located on the right side of the straight going arch bridge (2), with the right-turn bridge (3) being bifurcated from the straight going arch bridge (2) at the right-turn side, so as to form a Y-shaped bridge (1) bifurcating synclastically. All four bifurcated arch bridges are Y-shaped bridges (1) bifurcating synclastically. Two opposite Y-shaped bridges (1) bifurcating synclastically compose a group bridge, and two groups of one-way streets (8) for through traffic of two group bridges form a three-dimensional cross-shaped construction. The composite bridge or composite tunnel enables vehicles driving in four directions to pass a crossing freely.