CEMP-E
TI 850-02
AFMAN 32-1125(I)
1 MARCH 2000
Figure 6-27. Determining Frog Number (Turnout Size)
(2) Standard turnout sizes should be selected according to table 6-12.
Table 6-12. Turnout Size Selection Criteria
Turnout
Turnout
Curvature
Size
(Degrees)
Selection Criteria
10
7.4
Preferred where space permits, or where long cars (over 75 ft) or 140-ton flatcars
(with 3-axle trucks) are being handled. Use for crossovers.
9
9.3
Smallest size recommended for handling long cars (over 75 ft) or 140-ton flatcars
(with 3-axle trucks). In ladder tracks, saves space compared to a number 10.
8
11.8
Not recommended for handling long cars (over 75 ft) or 140-ton flatcars (with 3-
axle trucks). Smallest size normally permitted.
c. Design and Selection.
(1) The main design decisions for turnouts are the direction in which the turnout will diverge (as
shown in figure 6-25), and the angle of the frog (or frog number), which determines how sharply the
turnout diverges (and also designates the size of the turnout). Recommended choices for different
turnout components are covered below, as is layout design for use where nonstandard configurations are
required.
(2) Once a standard turnout has been selected from table 6-12, or the geometry has been otherwise
determined, the designer will then specify the desired switch, frog, and guard rails if needed, from the
appropriate AREMA plans; the turnout (or crossover) tie set from table 6-9; and the amount of rail needed
to complete the turnout (connect the switch and frog) from AREMA Plan 910 or 911. Guidance on the
selection of these items and other turnout hardware is given below.
(3) All materials used within the limits of a turnout will be factory designed and constructed, of the
proper type and size, and not be flame cut or otherwise altered in the field.
6-43
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