one direction opposition to that of the roadway 21 an overpass 24 crosses the road 1 and merges with the roadway 21 two ends of the overpass 24 are connected to the road surface of the roadway 21 the overpass 24 has an entrance 242 at one end and an exit 243 at the other end a bypass 241 is branched from the overpass 24 the bypass 241 is a strip an end 2411 of the bypass 241 connected to the road surface of the road 1 an overpass 25 crosses the road 1 and merges with the roadway 23 two ends of the overpass 25 are connected to the road surface of the roadway 23 the overpass 25 has an entrance 252 at one end and an exit 253 at the other end a bypass 251 is branched from the overpass 25 an end 2411 of the bypass 241 connected to the road surface of the road 1 the bypass 241 is defined by two arms and u shaped and the two arms are not in a same plane the arm connected to the overpass 25 is longer than the arm connected to the roadway 13 an intermediate section of the two arms is wider the two arms two entrances for u turn 221 and 222 are provided between the roadway 21 and the roadway 23 and on opposite side of the road 1 respectively the entrance for u turn 221 is spaced farther from the road 1 than the exit 253 so that a vehicle from the exit 253 can smoothly make a u turn the entrance for u.