Geometric Design and Highway Facilities Overview

Geometric design in transportation engineering involves components like roadway cross section, vertical and horizontal alignment, and roadside area. Horizontal alignment considers factors like centrifugal force and sight distance to ensure road safety. Different types of horizontal curves like simple, compound, reverse, and transition curves play a crucial role in designing highways.

• Transportation engineering
• Geometric design
• Highway facilities
• Horizontal alignment
• Road safety

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Presentation Transcript

1. CE 34500 Transportation Engineering Chapter 15: Geometric Design and Highway Facilities 1

2. Simple Curves

3. Geometric Design Geometric Design consists of four major components Roadway Cross Section Vertical Alignment Horizontal Alignment Roadside Area

4. Horizontal Alignment Tangent Sections Horizontal Curves o Design criteria Centrifugal Force: Resisted by friction force between tires & roadway and by component of vehicle s weight resulting from superelevation Sight Distance: Roadside obstacle must be far enough from edge of roadway to allow a driver to see far enough ahead to react and stop to avoid striking an obstacle in roadway (stopping sight distance)

5. Horizontal Alignment Centrifugal Force Criterion 2 u =15 R ( ) + e sf

6. Horizontal Alignment Horizontal Sight Distance Criterion

7. Horizontal Alignment Horizontal Sight Distance Criterion ? = ?(1 ???28.65 ?) ?

8. Horizontal Alignment Horizontal Sight Distance Criterion

9. Horizontal Curves Types of Horizontal Curves o Simple: single circular curve connecting two tangents o Compound: combination of two back-to- back circular curves in same direction with no tangent section between them (PCC) o Reverse Curve: same as compound curve, except curves are in opposite direction o Transition (Spiral): single circular curve with spiral curves (varying radii) at each end)

10. Simple Curves

11. Simple Curves = R 2 sin C 2 2 tan = 1 cos M R = R T 2 1 =R = 1 E R L 2 180 cos

12. Example 15.6 The intersection of a 40 curve is 55025 , and the PC is located at station 238+44.75. Determine the length of the curve, the station of the PT, the deflection angles, and the chord lengths for setting out the curve at whole stations from the PC. Figure 15.21 illustrates a layout of the curve.

13. Compound Curve

14. Reverse Curve

15. Transition (Spiral) Curves 3 . 3 15 u = L RC