Calculate curb radius, arc length, and sagitta from chord and offset, or find offset from radius and chord in ft, in, mm, cm, or m.

Curb Radius Calculator

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Chord + Offset
Arc + Offset
Radius + Chord

Find radius from chord and curb offset

Find radius from arc length and offset

Find offset and arc length from radius and chord

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Curb Radius Formula

The following formula is used to calculate the curb radius:

CR = VT / (tan(EA) + tan(XA))

Variables:

  • CR is the curb radius (feet)
  • VT is the vehicle trajectory (feet)
  • EA is the entry angle (degrees)
  • XA is the exit angle (degrees)

To calculate the curb radius, divide the vehicle trajectory by the sum of the tangents of the entry and exit angles.

What is a Curb Radius?

A curb radius is the curved edge of a roadway at an intersection or entrance to a roadway. It is designed to accommodate the turning path of vehicles, particularly larger ones like buses and trucks. A properly designed curb radius allows vehicles to make turns without encroaching on other lanes and ensures pedestrian safety by controlling the speed of turning vehicles.

How to Calculate Curb Radius?

The following steps outline how to calculate the curb radius:

  1. First, determine the vehicle trajectory (VT) in feet.
  2. Next, determine the entry angle (EA) in degrees.
  3. Then, determine the exit angle (XA) in degrees.
  4. Use the formula CR = VT / (tan(EA) + tan(XA)) to calculate the curb radius (CR) in feet.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

vehicle trajectory (VT) = 30 feet

entry angle (EA) = 25 degrees

exit angle (XA) = 25 degrees