A clear view screen is a disc inset in the viewing window of a boat, bus, train, or similar transport that remains clear of ice, condensation, mud, and other visual obstructions. The screen ensures that even in poor weather conditions, the operator will be able to see safely and can make steering decisions, including safely stopping the vehicle until it is possible to move freely again. Numerous companies manufacture clear view screens for insertion into existing windows, and they can also be built into a design from the start.
The clear view screen works by rotating in place to throw any detritus to the edges with the use of centrifugal force. The spin rate can vary, depending on the device, and an insulating gasket prevents fluid from leaking in around the sides of the clear view screen. Usually a small rotating arm spans the disc, but should not present a major visual distraction, especially for an experienced operator.
On a boat, the array of windows surrounding the bridge or wheelhouse may have several clear view screens to provide viewing opportunities from multiple positions. They are easy to identify from a distance, as the discs and their hardware will be clearly visible. Buses, trams, and locomotives can have similar screens mounted near the driver's line of sight for easy visibility in adverse weather conditions. Snow, sleet, salt spray, and hail can all potentially obscure an operator's view, as can deposits of ash from erupting volcanoes, major fires, and so forth.
Sometimes a clear view screen has heating to discourage condensation and ice buildups. This can be useful in extremely cold climates where there is a risk that the device might fog up, even though rotations will keep the surface mostly clear. Heating will prevent the development of ice crystals, limiting the chance that the whole screen will freeze over. The operator can turn the heating on and off, depending on conditions.
Installing a clear view screen can be helpful for any transport device likely to be used in bad weather conditions, especially if those conditions can onset suddenly. It can be critical to have a viewing window to stop boats and locomotives safely when the weather gets foul. When stopping or turning to avoid obstacles can take a long time because of size, weight, and speed, a clear view screen is necessary so operators know what they are doing. It will reduce the risk of collisions and other adverse events while underway.