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Above: Class 117 DMU built in the 1960s, capable of a top speed of 75mph (120 km/h)
This is one of the most popular types of railway vehicles on non-electrified line. The way it works is there is a diesel engine under each passenger carriage. They use the normal diesel-electric traction system.
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Above: Class 117 DMU built in the 1960s, capable of a top speed of 75mph (120 km/h) |
One advantage of these is that they are incredibly fuel-efficient. The diesels only need to roar up at stations to accelerate the train (sounding a bit like a bus) and once it is up to speed, because of the very low friction involved the engines can drop down to ticking over, which is all that's required to keep the train moving. (Unlike a road bus where the engine has to keep spinning at high revs).
Another advantage is the supply can be matched a lot better to demand, without affecting frequency of trains. Even in remote parts where there is very little demand for rail a train of just two carriges (or sometimes even just one) can be used which means reducing frequency of trains is not nessacary. In high density urban parts trains of 8 or even 12 cars can be used to cope with the numbers.
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Above: A 1980s 90 mph Class 158 DMU |
The majority of DMUs only have a top speed of 75 mph, ones built in the past 10 years (Class 158-166) can achieve 90 mph. For 1999 however all DMU to be ordered will be capable of 100mph (160km/h) and 9 High speed DMUs have been ordered which can travel up to 125 mph, which will be delivered in 1999. This DMUs may one day replace the Class 43 as the diesel high speed train Click here for a list of ordered trains
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Above: A 1990s Thames Turbo capable of 90 mph |
These trains keep railways alive in remote parts of scotland (there are no remote parts in England!) because they are as economical as buses, with all the advantages of travelling on railways (speed, comfort etc.)
The Thames Turbo is perhaps one of the better known trains, run by Thames Trains, these are the lastest trains with air conditioning!!?? (the UK isn't that hot!) and air suspension, which makes them remarkably smooth. These have been built in the 90s and use a lot of state of the art technology. A picture of this train is above.
A lot more Pictures of all the DMU classes can be found at: http://mercurio.iet.unipi.it/pix/gb/diesel/dmu/pix.html
