Navigating inland waterways presents unique challenges, and bridge clearance is one that every boater must understand. Collisions involving bridges are among the various risks boaters may encounter on inland waterways. Whether cruising beneath a fixed bridge or timing a passage beneath a movable bridge, boaters must understand their vessel’s height, the type of bridge ahead, and the signals that guide safe passage.

Passagemaker.com provides a comprehensive guide to navigating under bridges, designed to help boaters build confidence and ensure safe passage.

Know your boat:

• Measure your boat’s true air draft, from the waterline to its highest point, including added equipment like antennas or radar.
• It's important to assess bridge clearance carefully, as manufacturer-provided height measurements may not account for added equipment. Misjudging vertical clearance can lead to serious damage.

Understanding Bridge Types

• Fixed bridges: Typically have a clearance measurement of about 65 feet on major U.S. waterways, though some are built taller or shorter.
• Movable Bridges: Include swing, lift, bascule, and floating styles. Movable bridges operate either on request, a strict schedule, or a combination of both.
• Boaters should not expect bridge passage during rush hour or other peak traffic times.

Clearance and Gauges:

• Bridge clearance is based on mean higher high water, the highest expected tide level.
• Drawbridge clearance is measured at the lowest point of the span.
• Some bridges offer extra height near the center, but don't rely on it without checking.
• Clearance gauges, marked in one-foot increments, may be hard to read due to wear or marine growth.
• Bridge operators cannot see gauge readings and do not provide them. Boaters are responsible for ensuring safe passage.

Lights and Fender Systems:

• Overhead lights mark the safe channel for passing beneath bridges.
• Red and green light patterns vary by bridge. Refer to the Coast Guard’s Bridge Lighting Manual for specifics.
• Fender systems protect bridge supports and help guide vessels.
• Wait until the bridge is fully open and signal lights indicate it’s safe before entering the fender area.

Legal Obligations and Safety Protocols

• Requesting an unnecessary bridge opening is a federal violation and may result in fines up to $25,000.
• Lower antennas or gear, when possible, to safely clear bridges without raising them.

Navigating bridges safely means knowing your boat’s height, identifying the bridge type, and following signals and procedures. These steps help prevent damage and ensure safe passage.

This article is provided for general informational purposes only and does not constitute and is not intended to take the place of legal or risk management advice. Readers should consult their own legal counsel or other representatives for any such advice. Any and all third-party websites or sources referred to herein are for informational purposes only and are not affiliated with or endorsed by Intact Insurance Group USA LLC (“Intact”). Intact hereby disclaims any and all liability arising out of the information contained herein.

Intact Insurance Specialty Solutions, Intact Ocean Marine, and National Marine Underwriters are marketing brands for the insurance company subsidiaries of Intact Insurance Group USA LLC. Our solutions are backed by the financial strength of Atlantic Specialty Insurance Company, a subsidiary of Intact Financial Corporation (TSX:IFC), rated A.M. BEST A+ | FITCH AA | MOODY'S A1

Coverages may be underwritten by one of the following insurance companies: Atlantic Specialty Insurance Company, a New York insurer; Homeland Insurance Company of New York, a New York insurer; Homeland Insurance Company of Delaware, a Delaware insurer; OBI America Insurance Company, a Pennsylvania insurer; or OBI National Insurance Company, a Pennsylvania insurer. Each of these insurers maintains its principal place of business at 605 Highway 169 N, Plymouth, MN 55441.