Signal intersection left turning car flow organizing and designing method and road

The invention discloses a signal intersection left turning car flow organizing and designing method which sequentially comprises the following steps: setting a U-shaped going-through tunnel on each road on an intersection, wherein an opening of each U-shaped going-through tunnel faces the intersection, the U-shaped going-through tunnel comprises a down ramp, an up ramp and an arc-shaped tunnel, and the bottoms of the down ramp and the up ramp are connected through the arc-shaped tunnel; driving a car to a signal intersection, and turning right to the down ramp of the U-shaped going-through tunnel if the car needs to be turned left; turning the car which arrives the bottom of the down ramp left into the arc-shaped tunnel; driving the car to the bottom of the up ramp along the arc-shaped tunnel until to the top of the up ramp, i.e., a pavement, thus completing left turning of the car. For the method and the road disclosed by the invention, by preventing the car from turning left directly, possible conflict betw