RUNNING TRACK GRADE AND ALIGNMENT
Gradient. Track gradients are determined by the cost of
construction versus the operating costs. Naval facility trackage is usually
located in level terrain where gradient problems are non-existent or minimal.
Maximum design gradients should not exceed 3 percent compensated. Steeper
gradients, only up to 5 percent compensated, shall be approved by
NAVFACENGCOM. If a connecting railroad is to operate over Naval facilities,
discussions with the railroad should take place during the design phase
regarding gradients. See AREA Manual, Chapter 16, Part 1.
Curves. The type and character of equipment that must negotiate
the curves, available right of way, desired operating speed and traffic
density shall be considered in determining track curvature. The chord
definition for curves shall apply for railroad track.
Ruling Radii, Horizontal. For design of new tracks and for major
track rehabilitation the maximum degree of curvature shall be 16 degrees (359-
foot radius). If a tighter curve than 16 degrees (359-foot radius) is
required because of space limitations, prior approval must be obtained from
NAVFACENGCOM Headquarters. Larger radii, especially less than 10 degree
curves (574-foot radius), are desirable and every reasonable effort shall be
made to achieve such radii. A spiral curve is desirable between tangents and
curves and between the different radii of compound curves on Class 3 or higher
tracks. Spirals shall be according to AREA Manual, Spiral Curves, Chapter 5,
Part 3. Curves should be designed in terms of degree of curvature, and should
be whole degrees of curvature.
Reverse Curves. The minimum allowed tangent distance between
reverse curves, including crossovers, shall be according to the AREA Manual,
Chapter 5, Part 3, Reverse Curves. The desirable tangent distance between
reverse curves in yards and terminals should be 100 feet or more.
Vertical Curves. The maximum rate of change should be 0.20 foot
per 100 feet in sag curves and 0.40 foot per 100 feet on summit curves. For
tracks of lesser importance, such as sidings, rates of change can be
relatively large but not greater than practical considerations will permit.
Superelevation. Superelevation is generally not required on tracks
used at low speeds, i.e., in yards and sidings. Where required,
superelevation shall be computed per AREA Manual, Chapter 5, Part 3,
Elevations and Speeds for Curves. See AREA Manual, Chapter 5, Table 1 for
equilibrium elevations. An unbalanced elevation of 3 inches is recommended on
railroads where trains will operate at different speeds. Railroad track shall
not be superelevated where common with crane track.
Between parallel running tracks, 14 feet
Track Centerline Spacing.
shall be provided.