1 MARCH 2000
D = Degree of curve (decimal degrees).
R = Radius of curve (feet).
b. Design Criteria.
(1) Design categories for curves on main running tracks are shown in table 3-3; for terminals, also
use chapter 8, paragraph 3.
(2) During the design of major track rehabilitation projects, it is recommended that, where practical,
existing curvature above 10 degrees for main running tracks and 12 degrees in terminal areas be reduced
below these limits.
c. Minimum Tangent Length between Reverse Curves. When curves of different directions immediately
follow each other (reverse curves) there must be a length of tangent track between the two curves to
avoid train operating difficulties. The minimum tangent lengths between reverse curves are:
Degree of Curve
Minimum Tangent Length
6 - 12
(1) For either new design or major rehabilitation, the outer rail in curves should be elevated above the
inner rail by the amount shown in table 6-2. Designs should not call for a combination of speed and
curvature that fall below the bottom-stepped ledger line in the table.
(2) Full super-elevation must be provided around the entire curve. For curves with 1-in. super-
elevation, that elevation may be run out (transitioned back to level) in 40 ft of tangent at the beginning and
end of the curve. Where super-elevation is more than 1-in., spirals will be provided at each end of the
(1) When used, spiral transition curves will be designed as shown in chapter 5, part 3 of the AREMA
Manual. Super-elevation will uniformly increase from zero at the beginning of the spiral (at the tangent) to
the full elevation at the end of the spiral (where full curvature is reached).