Air draft
Air draft (or air draught) is the distance from the surface of the water to the highest point on a
Clearance below
The vessel's clearance is the distance in excess of the air draft which allows a vessel to pass safely under a
Mean Higher High Water
(MHHW).
In 2014, the United States Coast Guard reported that 1.2% of the collisions that it investigated in the recent past were caused by vessels attempting to pass under structures with insufficient clearance resulting in bridge strikes.[1]
Examples
The
Great Belt Bridge in Denmark). New vessels are rarely built not clearing 65 m (213 ft), a height which accommodates all but the largest cruise and container ships
.
The Suez Canal Bridge has a 70-metre (230 ft) clearance over the canal.
The Bayonne Bridge, an arch bridge connecting New Jersey with New York City, undertook a $1.7 billion modification to raise its roadbed to 66 m (217 ft).[5]
See also
- Structural clearance
- Structure gauge
- Tower Bridge
- Cargo ship size categories
- Chart datum
- Bridge strike
References
- ^ a b "Marine Safety Alert 090-14: AIR DRAFT IS CRITICAL!" (PDF) (Press release). United States Coast Guard Inspections and Compliance Directorate. 2014-09-09. Archived (PDF) from the original on 2022-05-16. Retrieved 2023-09-05.
- ^ 2104 Connecticut Boater's Guide (PDF). State of Connecticut Department of Energy and Environmental Protection. p. 60. Retrieved 2015-02-15.
- ^ See: NOAA Navigation Chart #12335, Hudson and East Rivers, Governors Island to 67th Street, Revised October 1, 2019, "HEIGHTS: Heights in feet above Mean High Water"
- ^ See: U.S. Coast Pilot 5, Chapter 8, p. 354, Structures across the Inner Harbor Navigation Canal, New Orleans, 15 December, 2019, "Vertical clearance measured at Mean High Water"
- ^ Bayonne Bridge rededication ceremony marks end of $1.7 billion project