Section 213.59 - Elevation of curved track; runoff(a) If a curve is elevated, the full elevation shall be provided throughout the curve, unless physical conditions do not permit. If elevation runoff occurs in a curve, the actual minimum elevation shall be used in computing the maximum allowable posted timetable operating speed for that curve under § 213.57(b) .(b) Elevation runoff shall be at a uniform rate, within the limits of track surface deviation prescribed in § 213.63 , and it shall extend at least the full length of the spirals. If physical conditions do not permit a spiral long enough to accommodate the minimum length of runoff, part of the runoff may be on tangent track.63 FR 34029, June 22, 1998, as amended at 78 FR 16101, Mar. 13, 2013