Growing competition from other modes of transportation has forced railway companies throughout the world to search for increased performance. Travelling time is the most obvious performance indicator that may be improved by introducing high-speed trains. Trains with capability to tilt the bodies inwards the curve is a less costly alternative than building new lines with large curve radii, which is needed for the non-tilted high-speed trains. Today, tilting has become a mature technology accepted by most operators, but not favoured by many. There are different reasons behind this fact; the non-tilting trains have increased their speed on curves (however at a reduced level of ride comfort), reducing the potential for travelling time reduction by tilting trains to approximately 10–15 per cent. The popularity is also affected by low reliability and motion sickness on certain tilting trains. Tilting trains can today be purchased from all the major train suppliers. The top speed of tilting trains follows the trend towards higher speeds. The first tilting train with top speed above 250 km/h will be set into service in 2007 in Japan, the Shinkansen N700. Track shift force may be critical for a high-speed tilting train and improved levels of track irregularities must be considered. The risk of overturning may give restriction on cant deficiency at high speeds. Evidence of motion sickness in both non-tilting and tilting trains has been and is still being reported. The sensory conflict is the most common explanation of motion sickness. The latest research suggests a model based on vertical acceleration. The model corresponds well to the hypothesis of motion sickness and can, together with suitable time dependence, describe the degree of motion sickness as function of time. The model is contradictory to earlier research which showed an optimum tilt angle different from zero. The running times improve with increased cant deficiency, top speed and tractive performance; however the benefit of increased top speed and tractive performance is small above a certain level. 15 minutes running time (9%) may be gained on the Swedish line Stockholm–Gothenburg if cant deficiency, top speed and tractive performance are improved compared with existing tilting trains. One interesting conclusion is that a non-tilting train will, independent of top speed and tractive power, have longer running times than a tilting train with today’s maximum speed and tractive power. Guidelines for installation of cant are given optimizing the counteracting requirements on good comfort in non-tilting trains and low risk of motion sickness in tilting trains. The guidelines are finally compared with the installed cant on the Stockholm–Gothenburg line. (Author/publisher)
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