 | This articleneeds additional citations forverification. Please helpimprove this article byadding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Bridge–tunnel" – news ·newspapers ·books ·scholar ·JSTOR(September 2014) (Learn how and when to remove this message) |
Abridge–tunnel is a persistent, unbrokenroad orrail connection across water that uses a combination ofbridges andtunnels, and sometimescauseways, and does not involve intermittent connections such asdrawbridges orferries.[1]
Bridge–tunnels are a form offixed link orfixed crossing which replaces ferry service. Fixed links are often, but not necessarily, intercontinental links between continents or transoceanic links to offshore islands.
For water crossings, a tunnel is generally more costly to construct than a bridge. However, navigational considerations at some locations may limit the use of high bridges ordrawbridge spans when crossingshipping channels, necessitating the use of a tunnel. Examples of such tunnels include theDowntown Tunnel andMidtown Tunnel under theElizabeth River betweenNorfolk andPortsmouth, Virginia in theUnited States, theGeorge Massey Tunnel inGreater Vancouver,Canada, and theCross-Harbour Tunnel underVictoria Harbour between the twin cities ofVictoria andKowloon inHong Kong.
In other instances, when longer distances are involved, a bridge–tunnel may be less costly and easier to ventilate than a single, lengthy tunnel. This situation may occur when more economicaldrawbridges are not allowed for one reason or another. For example, in theU.S. state ofVirginia, such crossings include theHampton Roads Bridge–Tunnel and theMonitor–Merrimac Memorial Bridge–Tunnel, both of which cross the harbor atHampton Roads, and theChesapeake Bay Bridge–Tunnel, a 37-kilometer-long (23 mi) structure (including approach highways) that crosses the mouth of theChesapeake Bay with a combination of bridges and tunnels across two widely separated shipping channels, using four artificial islands built in the bay as portals. Tunnels had to be used instead of drawbridges because the waterways they cross are critical to military naval operations (Naval Station Norfolk is nearby, and Chesapeake Bay provides access to thePotomac River and thus toWashington, DC) and could not afford to be blocked off by a bridge collapse in the event of disaster or war.
Another example is theØresund Bridge, connectingSweden andDenmark. It has a 7.8 km (4.8 mi) bridge, anartificial island in the middle of theØresund strait, and a 4 km (2.5 mi) tunnel nearest toDenmark. A bridge could not be built there for two reasons: height restrictions imposed by adjacentCopenhagen International Airport (the route's path passes the ends of some of the runways; the minimum practical height for a bridge would have interfered with airplanes using those runways) and the perennial threat of ice (a bridge's columns would have encouragedice dams which could block the strait).
TheTokyo Bay Aqua-Line is a bridge–tunnel combination acrossTokyo Bay inJapan. It connects the city ofKawasaki inKanagawa Prefecture with the city ofKisarazu inChiba Prefecture. With an overall length of 14 km (8.7 mi), it includes a 4.4 km (2.7 mi) bridge and 9.6 km (6.0 mi) tunnel underneath the bay—which is the longest underwater tunnel for cars in the world. Drawbridges were impractical here because Tokyo Bay is too active a sea lane.
Thelongest crossing on the Yangtze River in China is a tunnel-bridge-bridge complex, consisting of theShanghai Yangtze River Tunnel,Shanghai Yangtze River Bridge (one of thelongest cable-stayed bridges in the world),Chongming–Qidong Yangtze River Bridge and connecting viaducts at the river's mouth inShanghai. This fixed link carries theG40 Shanghai–Xi'an Expressway from the north bank to the south bank via two islands and is about 65 km (40 mi) in total length.
| Structural types |  | |
|---|---|---|
| Lists of bridges by type | ||
| Lists of bridges by size | ||
| Additional lists | ||
| Related | ||
