Tunnels and bridge.E2.80.93tunnels Bridge–tunnel

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for water crossings, tunnel more costly construct bridge. however, navigational considerations @ locations may limit use of high bridges or drawbridge spans when crossing shipping channels, necessitating use of tunnel. examples of such tunnels include downtown tunnel , midtown tunnel under elizabeth river between norfolk , portsmouth, virginia in united states , george massey tunnel in greater vancouver, canada.


in other instances, when longer distances involved, bridge–tunnel may less costly , easier ventilate single, lengthy tunnel. situation may occur when more economical drawbridges not allowed 1 reason or another. example, in u.s. state of virginia, such crossings include hampton roads bridge–tunnel , monitor–merrimac memorial bridge–tunnel, both of cross harbor @ hampton roads, , chesapeake bay bridge–tunnel, 37 km (23 mi) long structure (including approach highways) crosses mouth of chesapeake bay combination of bridges , tunnels across 2 separated shipping channels, using 4 artificial islands built in bay portals. tunnels had used instead of drawbridges because waterways cross critical military naval operations (naval station norfolk nearby, , chesapeake bay provides access potomac river , washington, dc) , not afford blocked off bridge collapse in event of disaster or war.


another example Øresund bridge, connecting sweden , denmark. has 7.8 km (4.8 mi) bridge, artificial island in middle of Øresund strait, , 4 km (2.5 mi) tunnel nearest denmark. bridge not built there 2 reasons: height restrictions imposed adjacent copenhagen international airport (the route s path passes ends of of runways; minimum practical height bridge ve interfered airplanes using runways) , perennial threat of ice (a bridge s columns have encouraged ice dams block strait).


the tokyo bay aqua-line bridge–tunnel combination across tokyo bay in japan. connects city of kawasaki in kanagawa prefecture city of kisarazu in chiba prefecture. overall length of 14 km (8.7 mi), includes 4.4 km (2.7 mi) bridge , 9.6 km (6.0 mi) tunnel underneath bay—which longest underwater tunnel cars in world. drawbridges impractical here because tokyo bay active sea lane.


the longest crossing on yangtze river in china tunnel-bridge-bridge complex, consisting of shanghai yangtze river tunnel, shanghai yangtze river bridge (one of longest cable-stayed bridges in world), chongming–qidong yangtze river bridge , connecting viaducts @ river s mouth in shanghai. fixed link carries g40 shanghai–xi expressway north bank south bank via 2 islands , 65 km (40 mi) in total length.







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