Design of curves

Transportation Engineering

1. DESIGN OF CURVES DOLAT RAM (15CRP 25 ) Mehran University of Engineering and Technology , Jamshoro

2. CURVES Curves are regular bends provided in the lines of communication like roads, railways etc . They are classified into two main types: Horizontal curve Vertical curve

3. HORIZONTAL CURVE A horizontal curve provides a transition between two tangent strips of roadway, allowing a vehicle to negotiate a turn at a gradual rate rather than a sharp cut . The design of the curve is dependent on the intended design speed for the roadway, as well as other factors including drainage and friction .

4. Classification of Horizontal Curves Horizontal curves are commonly classified into 4 types : i ) Simple Curve ii) Compound Curve iii) Reverse or Serpentine Curve iv) Spiral or Deviation Curve

5. Simple, Compound, Reverse and Spiral Simple Curve - Curve with single constant radius. Compound Curve – Two or more curves in succession, turning in the same direction. Reverse Curve – Two simple curves with equal radii turning in opposite directions with a common tangent. Spiral or Deviation Curve – Also called transition curves; placed between tangents and circular curves or between two adjacent circular curves having substantially different radii.

6. VERTICAL CURVE A vertical curve provides a transition between two sloped roadways, allowing a vehicle to negotiate the elevation rate change at a gradual rate rather than a sharp cut . The design of the curve is dependent on the intended design speed for the roadway, as well as other factors including drainage , slope , acceptable rate of change , and friction .

7. COMPONENTS OF A CURVE R RADIUS PC POINT OF CURVATURE PT POINT OF TANGENCY POC POINT OF CURVE PI POINT OF INTERSECTION L LENGTH OF CURVE T TANGENT DISTANCE LC LONG CHORD E EXTERNAL DISTANCE M MIDDLE ORDINATE D DEGREE OF CURVE I DEFLECTION ANGLE

8. FORMULAS FOR SIMPLE CURVE  

9. STOPPING SIGHT DISTANCE Stopping Sight distance is one of several types of sight distance used in road design. It is a near worst-case distance a vehicle driver needs to be able to see in order have room to stop before colliding with something in the roadway, such as a pedestrian in a crosswalk, a stopped vehicle. Insufficient sight distance can adversely affect the safety or operations of a roadway or intersection .