1 Superelevation and Spiral Curves
2 Source: A Policy on Geometric Design of Highways and Streets (The Green Book). Washington, DC. American Association of State Highway and Transportation Officials, th Ed.
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5 Source: CalTrans Design Manual online,
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, th Ed.
7 Source: Iowa DOT Standard Road Plans RP-2 With Spirals Same 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, th Ed.