Movable bridges accommodate vessel traffic and land traffic, avoiding the need for expensive high bridges. Designs include seesaw, vertical lift, swing span, and retractable bridges. Operators monitor vessel traffic and consider traffic management issues.
Movable bridges are bridges with components that change position to accommodate vessel traffic. These bridges can be seen in many regions where transportation officials balance the need for bridges to allow trains, cars, and trucks to pass with the desire to accommodate ships. The alternative would be to build an extremely high and expensive bridge so that ships can pass underneath while land traffic passes over, and this may not always be an option.
Humans have used movable bridges over waterways for centuries, and a number of basic designs are in use. One of the most familiar is the seesaw, also known as a drawbridge, in which one or both sides of a bridge are attached on a hinge and can pivot upward to create an opening large enough for a boat. Some movable bridges curl or bend rather than rotate, depending on the design. This basic mobile bridge is easy to install and use and is very popular.
Vertical lift bridges move the roadway platform or rails on the posts so ships can pass underneath, while swing span bridges pivot outward and sideways to create an opening. You can also see retractable bridges, with panels that retract for passing traffic. The variation in designs for movable bridges can accommodate different environments and needs. Engineering firms specializing in these types of projects can draw on a library of bridge designs and styles to determine the best choice for a given application.
An operator on a bascule bridge monitors vessel traffic and determines when to move the bridge and how long to keep it open. Typically an alarm system is activated first, with lights, audible warnings and drop-down gates to encourage cars to get off the bridge and stay away. Once the bridge is free, the operator can activate the system to move it. After the ship has passed, the position of the bridge can be reset.
Traffic management with mobile bridges can be complicated. Operators may need to consider issues such as how opening a bridge will affect peak hour traffic or maximum clearance under the bridge. Very large boats may have to pass at low tide, for example, even with the deck open, because their superstructures may overhang the waterline. Ground traffic could be increased by sporting events and other issues, making it necessary to consider keeping vessels on movable bridges to avoid a snag of ground traffic.
Protect your devices with Threat Protection by NordVPN
