Pontoon bridge using a single 'o'. The U.S. military differentiated between the bridge itself ("ponton") and the floats used to provide buoyancy ("pontoon"). The original word was derived from Old French "ponton", from Latin "ponto" ("ferryboat"), from "pons" ("bridge"). When designing a pontoon bridge, the civil engineer must take into consideration the Archimedes' principle: Each pontoon can support a load equal to the mass of the water that it displaces. This load includes the mass of the bridge and the pontoon itself. If the maximum load of a bridge section is exceeded, one or more pontoons become submerged. Flexible connections have to
Cable barrier several types of highway barrier did not find an appreciable difference in fatal and severe injuries between cable barrier and W-beam barrier. Both were significantly more hazardous than concrete barrier, however were less hazardous than having no barrier at all. There are two types of cable barrier systems in use today, low-tension and high-tension. Each system has its advantages and disadvantages, but in general, a high-tension system has a higher initial cost with lower long-term maintenance costs and concerns. During the expansion of cable barrier use throughout the 1980s and 1990s, the low-tension system was specified almost exclusively. This system