Arakawa Peil
This is the Tatsumi Bridge in Koto-ku, Tokyo.
Can you see the AP+6.0m on the right side of the bridge?
AP is one of the standards for the water level in Tokyo Bay, and it refers to the Arakawa Peil.
This bridge tells passing ships that it is 6 meters higher than the Arakawa Peil as an indicator.