Curves
Horizontal and vertical curves.
Road and rail geometry: horizontal circular curves, spiral transitions, curve staking tables, equal- and unequal-tangent vertical curves, and vertical curve length for sight distance. It is for survey crews staking alignments and engineers checking plans. Start with the circular curve tool or the vertical curve tool. Check whether a degree of curve uses the arc or the chord definition before turning it into a radius, because the two give different curves.
I want to lay out a horizontal curve
- Horizontal circular curve
All elements of a simple circular curve (radius, deflection, tangent, length, chord, external, middle ordinate, degree of curve) from any two, with PC and PT stations.
I want to lay out a spiral transition
- Spiral-curve-spiral transition
The elements of a clothoid spiral-curve-spiral (spiral angle, X, Y, p, k, long and short tangents, total tangent), its TS, SC, CS, and ST stations, and deflections along the spiral.
I want to stake out a curve at a station interval
- Circular curve layout table
PC and PT stations for a circular curve and a layout table at a chosen interval: station, deflection from the PC, chords, and coordinates when the PI position and back tangent are given.
I want to design a vertical curve
- Vertical curve
PVC and PVT stations and elevations, the high or low point, and the K value of a symmetric parabolic vertical curve.
- Unequal-tangent vertical curve
A vertical curve with different tangent lengths each side of the PVI: PVC, PVT, and the point under the PVI, the high or low point, and the elevation at any station.
I want to size a vertical curve for sight distance
- Vertical curve length for sight distance
The shortest crest or sag vertical curve that gives a sight distance, from the standard formulas with your eye, object, or headlight heights, stating which case applies; design values come from your design manual.