The invention relates to a left-side-driving combined traffic facility of Y-shaped bifurcated bridges and Y-shaped bifurcated tunnels. According to the invention, two independent bifurcated arch bridges and two independent bifurcated tunnels are combined into a crossroad traffic facility which contributes to unobstructed transportation. A Y-shaped co-directional bifurcated bridge is formed by a straight-driving arch bridge and a right-turning bridge positioned on the right side of the straight-driving arch bridge. Two bifurcated bridges with opposite bifurcations form a bridge set. A Y-shaped co-directional bifurcated tunnel is formed by a straight-driving tunnel and a right-turning tunnel positioned on the right side of the straight-driving tunnel. Two bifurcated tunnels with opposite bifurcations form a tunnel set. Two straight bridge one-way sections of the bridge set and two straight tunnel one-way sections of the tunnel set form a stereo cruciform structure. With the combined traffic facility, damage degrees of local geological changes to the combined bridge can be reduced. A left-turning bridge and a right-turning bridge share a same bridge, and a left-turning tunnel and a right-turning tunnel share a same tunnel. Lane merging sections are long, such that obstruction is not easy to occur. Vehicles can turn right directly without unnecessary circulation. Pedestrians can pass under the combined bridge. With the combined traffic facility, complete intercommunication of a bidirectional six-lane small crossroad can be realized.