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How to Calculate Superelevation for Horizontal Curves Using Excel

Superelevation is the tilting of the roadway surface to help offset the centripetal forces that act on a vehicle as it goes around a curve. Superelevation, along with friction, helps to prevent the vehicle from skidding or overturning. The amount of superelevation depends on factors such as the design speed, the radius of curvature, and the coefficient of friction.

One way to calculate superelevation for horizontal curves is to use an Excel spreadsheet that follows the guidelines of the American Association of State Highway and Transportation Officials (AASHTO) 2011 Green Book. The spreadsheet can also calculate the tangent runout and spiral information for transition curves.

In this article, we will show you how to use the spreadsheet Horizontal Curve (Superelevation Calculation Sheet).xls [^2^] to perform these calculations. You can download the spreadsheet from this link: Horizontal Curve (Superelevation Calculation Sheet).xls

Steps to Calculate Superelevation for Horizontal Curves Using Excel

1. Open the spreadsheet Horizontal Curve (Superelevation Calculation Sheet).xls and enable macros if prompted.
2. Enter the design speed, radius of curvature, coefficient of friction, and lane width in the input section. You can also choose the units (metric or English) and the method of superelevation distribution (normal crown or full superelevation).
3. The spreadsheet will automatically calculate the superelevation rate, tangent runout length, spiral length, and other parameters in the output section. You can also see a graphical representation of the horizontal curve and its elements.
4. You can print or save the spreadsheet for future reference or use.

Conclusion

Calculating superelevation for horizontal curves is an important step in highway design. It helps to ensure the safety and comfort of drivers and passengers. Using an Excel spreadsheet like Horizontal Curve (Superelevation Calculation Sheet).xls can simplify this task and save time and effort. You can download the spreadsheet from this link: Horizontal Curve (Superelevation Calculation Sheet).xls

If you need more information on superelevation tables or other highway design tools, you can visit this website: Superelevation Tables | FHWA

Examples of Superelevation Calculation for Horizontal Curves Using Excel

To illustrate how to use the spreadsheet Horizontal Curve (Superelevation Calculation Sheet).xls, let’s look at some examples of superelevation calculation for different scenarios.

Example 1: Normal Crown Method, Metric Units

Suppose we want to design a horizontal curve with a design speed of 100 km/h, a radius of curvature of 500 m, a coefficient of friction of 0.15, and a lane width of 3.6 m. We also want to use the normal crown method and metric units for our calculations.

We enter these values in the input section of the spreadsheet and select the normal crown option and the metric units option. The spreadsheet will calculate the following values in the output section:

• Superelevation rate: 0.06 or 6%
• Tangent runout length: 21.6 m
• Spiral length: 43.2 m
• Central angle: 57.3 degrees
• Curve length: 500 m
• External distance: 14.4 m
• Mid-ordinate distance: 7.1 m
• Long chord: 493.3 m

We can also see a graphical representation of the horizontal curve and its elements in the spreadsheet.

Example 2: Full Superelevation Method, English Units

Suppose we want to design a horizontal curve with a design speed of 60 mph, a radius of curvature of 1500 ft, a coefficient of friction of 0.12, and a lane width of 12 ft. We also want to use the full superelevation method and English units for our calculations.

We enter these values in the input section of the spreadsheet and select the full superelevation option and the English units option. The spreadsheet will calculate the following values in the output section:

• Superelevation rate: 0.08 or 8%
• Tangent runout length: 96 ft
• Spiral length: 192 ft
• Central angle: 34.4 degrees
• Curve length: 900 ft
• External distance: 48 ft
• Mid-ordinate distance: 23.6 ft
• Long chord: 887.4 ft

We can also see a graphical representation of the horizontal curve and its elements in the spreadsheet.