One thing that interested me was Shimanto river, which is considered one of the purest river in Japan. The river is close to nature, less controlled by humans, and rich in traditional Japanese scenery. I was actually moved by the landscape surrounding Shimanto river.
Over the river, there were some unique bridges that had no side walls on he bridge. No wonder that lack of side walls put passengers and cars crossing the bridge at risk for falling into the water. It seems, however, that the structure is useful for the bridge to protect itself from breaking down when a massive flood occurs.
I have heard that a bridge like that is called "Chinka bashi", meaning "able to get under the water for safety in the situation of increasing in river water." I am not 100% sure if this theory works on practice, but there is no doubt that crossing this bridge by car makes the driver feel uneasy.
Take a look at the left lower panel, where we are going over the bridge with our car. I could see anything but the surface of the river through the side windows of the car, because the bridge had no protect side wall. What was worse was the width of the bridge, which was almost as wide as that of a family car. This can explain the reason why the trial scared me (I am not a coward), although my three kids were excited.
I guess that we should not have crossed the river by car because a car itself would not be suitable to such a beautiful nature.