What is Vertical-lift bridge?
[[File:MovableBridge lift.gif|thumb|right|250px|{{Center|Lift bridge}}]] A '''vertical-lift bridge''' or '''lift bridge''' is a type of [[Bridge|movable bridge]] in which a [[span (architecture)|span]] rises [[vertical]]ly while remaining [[parallel]] with the [[road]] surface. The vertical lift offers several benefits over other movable bridges such as the [[bascule bridge|bascule]] and [[swing bridge|swing-span bridge]]. They are generally easier to [[design]] and easier to build.<ref name=Koglin76>Terry L. Koglin, ''Movable Bridge Engineering'' (Hoboken, NJ: J. Wiley & Sons, 2003), p. 76</ref> They usually cost less to build for longer moveable spans.<ref>Leonardo Fernandez Troyano, ''Bridge Engineering: A Global Perspective'' (London: Telford, 2003), p. 731</ref> The [[counterweight]]s in a vertical lift bridges are only required to be equal to the weight of the deck.<ref name=Koglin76/> Bascule bridge counterweights must weigh several times as much as the span being lifted. As a result, heavier materials can be used in the deck, and so this type of bridge is especially suited for heavy railroad use.<ref name=Koglin76/> Although most vertical-lift bridges use [[Bridge tower|towers]], each with counterweights. Some use [[hydraulic jack]]s located below the deck. An example is the {{convert|52|ft|m|adj=on}} span bridge at St Paul Avenue in [[Milwaukee]], [[Wisconsin]], [[USA]].<ref>Leonardo Fernandez Troyano, ''Bridge Engineering: A Global Perspective'' (London: Telford, 2003), p. 729</ref> Another design used [[wikt:balance|balance]] [[beam (structure)|beam]]s to lift the [[wikt:deck|deck]] with pivoting bascules located on the top of the lift towers.<ref>Leonardo Fernandez Troyano, ''Bridge Engineering: A Global Perspective'' (London: Telford, 2003), p. 732</ref> An example of this kind is the [[La Salle Street Bridge (Chicago, Illinois)|La Salle Street Bridge]] in [[Chicago]], [[Illinois]], USA. The biggest disadvantage to the vertical-lift bridge is the height [[wikt:restriction|restriction]] for [[ship