They arent used as much because we have new kinds of bridges that may be more efficient and that are stronger
The superlative of efficient is "most efficient."
Germany has most bridges
Spur Gear is the most efficient
More efficient and most efficient are the comparative and superlative forms of "efficient".
Brooklyn bridges most major attractions are during christmas :)
A screw is the most efficient.
The most common materials used in bridge building are generally steel or concrete for larger bridges, and stone or wood for smaller bridges.
ATP is the most efficient molecule
Heat is the most efficient agent of metamorphism.
In the colonial days of North America, there were few roads that were safe or reliable, and no bridges to cross the frontier rivers. The most efficient way to transport goods was by boat, and the majority of goods were carried to ports downstream, as it was much harder to travel upriver.
most cost-efficient