In the three boxes below, EITHER enter the Radius of Curvature on its own, OR enter any TWO of the following three values.
If the road is straight (no curvature), then check this box:
Otherwise, enter the radius of curvature (metres):
Chord Length (metres):
Middle Ordinate:
OPTIONALLY, if you wish to take into account the vertical profile of the road, such as at the brow or base of a hill, use surveyed data to determine the vertical radius of the curvature of the road, and change the default value (Infinity) to that radius here. A convex surface, or hill brow will have a positive radius. A concave surface or dip will have a negative radius. The default value of Infinity is used for a surface which is level or has a constant longitudinal gradient.
Optional Vertical Radius of Curvature (metres):
Now enter any TWO of the following values:
Coefficient of Friction:
Camber (degreees):
Critical Speed:
Now click the Calculate button to calculate the above missing values.
If you wish to calculate the Braked Critical Speed, you must first have all of the values calculated as per the instructions above, then enter the Deceleration Rate in the box below and click the Calculate Braked Critical Speed button.
Deceleration Rate:
Braked Critical Speed (m/s):
G.R.Greatrix, Critical speed under braked conditions, Impact, 11, 2, 2002.
G.R.Greatrix, Critical speed at the brow of a hill, Impact, 8, 2, 1999.
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