How to Figure a Delta Angle
- 1). Refer to Figure 1 from the horizontal curves resource document located at http://www.iowadot.gov/design/dmanual/02a-01.pdf to get a visual representation of how to determine or measure L or LC. L is the total length in feet of the circular curve from the point of curvature, or "PC", to the point of tangency, or "PT" measured along its arc. Determine or measure L of the curved shape configuration from which you are looking to calculate the delta angle. As an example, assume L is 25 feet.
- 2). Refer to Figure 1 from the horizontal curves resource document located at http://www.iowadot.gov/design/dmanual/02a-01.pdf to get a visual representation of how to determine or measure R. R is the radius of the circular curve measured in feet. Determine or measure R of the curved shaped configuration from which you are looking to calculate the delta angle. As an example, assume R is 25 feet.
- 3). Calculate the delta angle using the formula: Delta = (180L)/(3.1415R). Using the above examples, the delta angle will be 52.3 ((180 x 25ft)/(3.1415 x 25ft)) degrees.
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