Quote:
Originally Posted by M1EK
DMUs are a really stupid idea if you want to get where the people are; they typically have turning radii more like freight trains than like what most people call light rail vehicles.
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True. But you must admit the soon to be abandoned UP rail corridor had freight trains on it! Having a turning radius of a freight train works in this instance!
While it is nice to have a train that can make sharper turns when needed in a pinch, just because it can isn't a good reason to turn sharply. On the east side of downtown Dallas, Dart recently took out some very sharp "S" turns so the trains can run faster. They ended up cutting diagonally through a city block. Lucky for them, it was a vacant lot.
What determines the turning radius of any vehicle is its wheelbase, the distance between the front and rear wheels. Dart's light rail cars have a wheelbase of ~30 feet. Standard rail passenger cars have a wheelbase between 60 and 70 feet. Of course longer wheelbase vehicles can't turn as sharply. Just like a stretched Lincoln Towncar can't turn as sharply as the standard sized sedan model. CapMetro's DMUs have an effective wheelbase of ~41.5 feet. DMUs can be built with shorter wheelbases. Stadler could build a shorter train with a shorter wheelbase if that was the technical demands of your route.
From
http://www.dart.org/about/inmotion/summer07/6.htm
Quote:
Straight to the Future
The old "S" curve that slows DART Rail trains entering and exiting the downtown portal of the subway under North Central Expressway is being replaced with a straighter rail configuration that will speed train trips and lower maintenance costs.
Staged with a series of highway and street improvements on the northeastern edge of the Central Business District, DART's Bryan-Hawkins Project also will make way for a smooth connection to the new Green Line that will link downtown to Deep Ellum, Fair Park, South Dallas and Pleasant Grove. The Green Line, which begins a phased opening in September 2009, also features a Northwest Corridor serving Victory Station, the Dallas Market Center, Southwestern Medical District, Love Field Airport area, Farmers Branch and Carrollton.
The Bryan-Hawkins Project began this summer with the removal and reconstruction of the retaining wall extending from the south subway portal. Work in the area is expected to continue through June 2009.
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Photo from DART
Even on the old sharp "S" curve route, Dart had to round the corners off. It was
cheaper for Dart in the long run to cut diagonally through the block than to go around.
Other transit agencies have learned this lesson too. Look how Norfolk's Tide light rail plans to cut through a city block instead of going around. Another You Tube video:
http://www.ridethetide.com/stationov...erstation.html
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