Conversion: 1 mi/h 1.609 km/h.
General notes:
1. The Lr in Tables 2.12 and 2.13 is the same as L in Table 2.14 and is based on a two-lane 24-ft pavement
revolved about the centerline.
2. Adjustments to L for varying two-lane pavement widths can be made by direct proportion. For a 20-ft pavement
revolved about the centerline, L L(20/24).
3. Determination of X, L, and T when more than one lane is revolved about the centerline (or other reference
line, such as a baseline or edge of pavement) is shown in part (c). Values for G and B in the formulas are given in
parts (a) and (b), respectively. The value for W is the pavement width from the point of rotation to the farthest edge.
4. The minimum length of superelevation transition (X) as discussed in the text is the distance traveled in 2 s.
This number can be rounded off to a figure in feet equal to 3 times the design speed. In part (d) the calculated X
value is compared to the value of 3D, where D is the linear feet equivalent of the design speed in miles per hour. If
the value of 3D is larger, X is set equal to this value and L and T are adjusted accordingly.
5. The L value is also the recommended spiral length where spirals are used.