For reasons that will be mentioned below, passenger vehicles usually traverse a curve at a speed higher than the balance speed. The amount by which the actual speed exceeds the balance speed is conveniently expressed via the so-called cant deficiency, i.e., by the amount by which the superelevation would need to be increased to raise the balance speed to the speed at which the vehicles actually travel. Letting "gaugese" denote the rail gauge from low rail gauge side corner to high rail field side corner, letting "super_el" denote the actual superelevation, and letting "Vact" denote the actual speed, it follows from the definition that the cant deficiency, "CD", is given by the formula