Horizontal Curves

CEMP-E

TI 850-02

AFMAN 32-1125(I)

1 MARCH 2000

5730

Eq 6-2

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

0-6

60 ft

6 - 12

100 ft

d. Super-elevation.

(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

curve.

e. Spirals.

(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).

6-6