1

Superelevation and Spiral Superelevation and Spiral CurvesCurves

Superelevation and Spiral Superelevation and Spiral CurvesCurves

2

Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC. American Association of State Highway and Transportation Officials, 2001 4th Ed.

3

Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC. American Association of State Highway and Transportation Officials, 2001 4th Ed.

4

5Source: CalTrans Design Manual online, http://www.dot.ca.gov/hq/oppd/hdm/pdf/chp0200.pdf

6

Maximum Relative Gradiant (G)

Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC. American Association of State Highway and Transportation Officials, 2001 4th Ed.

7Source: Iowa DOT Standard Road Plans RP-2

With SpiralsSame as point E of GB

8

Source: Iowa DOT Standard Road Plans RP-2

With Spirals

Tangent runout (A to B)

9

Source: Iowa DOT Standard Road Plans RP-2

With Spirals

Removal of crown

10

Source: Iowa DOT Standard Road Plans RP-2

With Spirals

Transition of superelevation

Fully superelevated

11

Length of Components (Cont.)

Length of Runoff: function of design speed, rate of attainment, and width of lanes – See Exhibit 3-29 p. 174 for two and four lane highways (based on appearance and comfort)

Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC. American Association of State Highway and Transportation Officials, 2001 4th Ed.