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  • 2005-05-29 (xsd:date)
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  • Tunnel Vision (fi)
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  • Example: [Collected on the Internet, 2004] Isn't this one of the neatest things you have seen? This bridge is half under the water, for ships to pass and then again, it comes out on the other side. Truly a marvelous piece of engineering! This bridge is between Sweden and Denmark ... Picture taken from the side of Sweden.The bridge (or should it be called tunnel) goes under water to allow movement of ships.Origins: This is a case where a photograph of a remarkable object is real enough, but someone has mistakenly placed the subject nearly half a world away from its true location. The structure pictured above is genuine, but it's nowhere near Scandinavia. It is actually the Monitor-Merrimac Memorial Bridge-Tunnel (MMMBT), a 4.6-mile long combination bridge-tunnel system (named for the two ironclad ships that fought in the Hampton Roads harbor during the Civil War) connecting two Virginia communities across the mouth of the James River. The MMMBT opened in April 1992 after seven years of construction and a total cost of about $400 million. (Fabricating the tunnel portion of the bridge and lowering it into place cost $126 million alone.) As described on Scott M. Kozel's informative Highway and Transportation History web site (the source of the aerial photograph displayed above): The tunnel is 4,800 feet long from portal to portal, and it was built by the immersed sunken tube method, comprised of 15 prefabricated segments each 300 feet long and with two 2-lane bores, placed by lay-barges and joined together in a trench dredged in the bottom of the harbor, and backfilled over with earth. Four percent (4%) maximum grades are utilized in the tunnel, and a 60 mph design speed. The traffic lanes in the tunnel are 13 feet wide, with 2.5-foot-wide ledges on either side of the roadway, and with 16.5 feet of vertical clearance from the roadway to the ceiling. The current shipping channel above the deepest part of the tunnel has 800 feet of horizontal width and 45 feet of vertical depth below the average low-tide water level, and the tunnel was designed and built deep enough to allow for a future enlargement of the shipping channel to 1,000 feet of horizontal width and 55 feet of vertical depth below the average low-tide water level.According to the Virginia Department of Transportation (VDoT), the MMMBT incorporates many technological features to provide motorists with a safe and smooth driving experience, including: Traffic flow is monitored from a traffic management center where employees keep an eye on operations through 33 closed-circuit television cameras. Incidents can be detected immediately and assistance dispatched from two emergency response garages. Seventy-two sensors in the pavement of the tunnel and approach bridges automatically check every 20 seconds for interruptions in traffic flow. In the event of an incident, motorists are advised of alternate routes via 32 electronic message signs activated immediately from the traffic management center.While traveling through the Monitor Merrimac, motorists do not lose their favorite local radio station while in the tunnel. A communications system rebroadcasts all local AM and FM radio stations. In the event of an emergency, tunnel staff can override these broadcasts with emergency information motorists receive through their vehicle's radio without changing stations.The Øresund Link, a somewhat similar bridge-tunnel system between Sweden and Denmark, opened in 2000, and evidently someone mistook a photograph of one for the other. (en)
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