Its a train the tilts when going round corners. Britains railway lines were laid at a time when trains went at very slow speed and tight bends were OK, but fast trains cannot go around such bends. The choice of relaying all railway tracks as straight lines with gently curves is not possible in this overcrowded island, so the alternative is to shift the centre of balance of the train be tlting on a bend. However the first trains in the '80s were not successful. Virgin are trying again. See http://www.bbc.co.uk/northyorkshire/travel/story/t ilting_train/index.shtml
for more info
Actually, most trains can quite happily go round sharp curves. The main reason for tilt trains is so the poor passengers don't feel even more uncomfortable due to G forces etc. A machine is much more forgiving!