1. Wisconsin DOT Facilities Development Manual (FDM)
Weston Philips 1/27/05

2. Superelevation
Vertical Alignment

3. Superelevation

4. A different angle on superelevation?
Ch. 3 Elements of Design
In Horizontal Alignment Section
p. 173
Ch. 2 Alignments
Section 2A-2, 2A-3

5. Axis of Rotation Rotate pavement about centerline
Rotate about inner edge of pavement
Rotate about outside edge of pavement
Rotate about center of median (Divided)

6. Axis of Rotation

7. Axis of Rotation

8. Superelevation Profile
Two-Lane Highway – Centerline Rotation

9. Normal Crown

10. Tangent Runout/Crown Runoff
Horizontal

11. Superelevation Runoff
Superelevation = Cross Slope

12. Superelevation Achieved

14. Max Superelevation Rate
Nomograph (Discussed Later)

15. Max Superelevation Rate Cont’d

16. How to Calculate Superelevation
Using Superelevation Tables
Nomographs
Simple Curve Formula

17. Superelevation Option 1
Given: VD = 40 mph
R = 700 ft.
fmax = (from Table 7)
First solution is obtained from the superelevation tables, emax = 0.04 (Figure 9)
R = 700.; e = 0.039
3.9%
Note: Choose Table emax = 0.04

18. Iowa has ramp tables.

20. Minimum Radius
Greenbook p. 145 (186 pdf)
Minimum Radius Table

21. Superelevation Option 2
Radius
700 feet
e = -2.5%
40mph

22. Note: Greenbook contains derivation of equations/graphs.

23. Superelevation Option 3
Third solution is obtained from the simplified curve formula:
e = (VD2/15R) - fmax (English version)
e = (402/15*700) = =
-2.56%
Where:
VD = design speed
R = radius
e = superelevation rate
fmax= maximum side friction.
Note: Metric Version
e = (VD2/127R) - fmax (metric version).

24. Superelevation Transition
Superelevation transition is the length required to rotate the cross slope of a highway from a normal crowned slope to a fully superelevated cross slope.

25. Transition Placement
WisDOT practice is to place the tangent runout and approximately two-thirds of the length of runoff on the tangent approach and one-third of the length of runoff on the curve.

26. Calculations
Compute the theoretical point of normal crown and the theoretical point of full superelevation.
Given:
PC = Station
L = 115 ft. (Table 7, 40mph design speed)
X = L * NC/ e = 115 * .02/.02 = 115ft
Theoretical point of normal crown
PC - 2/3L - X = =
Station
Theoretical point of full superelevation
PC + 1/3L = =
Station
Where:
PC = Point of Curvature
L = Length of Runoff
X = Length of Tangent Runout
NC = Normal Crown of 2%

27. Length of Runoff (L)

28. Length of Runoff (L)
The adjustment factor (α) is used to adjust for different roadway widths.

30. Length of Runoff (L)
Greenbook p. 171 (pdf 212)

31. Tangent Runout Lt or X

32. Tangent Runout Lt or X

33. Tangent Runout Lt or X

34. Tangent Runout Lt or X

35. Vertical Alignment

36. The highway vertical alignment consists of tangents or grades and vertical curves.
Design vertical curves to provide adequate sight distance, safety, comfortable driving, good drainage, and pleasing appearance.

37. No Vertical Curves?
“Although grade changes without a vertical curve are discouraged, there may be situations where it is necessary.”
“Some rounding of the deflection point is anticipated during construction.”

38. Max % Grade By Functional Class

39. K Vertical Curves Vertical curves are generally
identified by their K values.
K is the rate of curvature and is defined as the length of the vertical curve divided by the algebraic difference in grade
Note: For Drainage, use K > 167 K

40. Question: Is there more on Vertical Alignment in the Wisconsin Manual?
p. 235 (276 pdf)