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 In many ways, horizontal alignment is an art form. The goal is to produce a horizontal curve that is comfortable and safe to use, and also cost efficient and aesthetically pleasing. The first step is to calculate the radius of the horizontal curve. We can calculate the radius for any combination of superelevation and side-friction factors using the equation below. R = V2/(127(e/100+f)) Where: As long as the radius of your curve is above the minimum radius as described in the minimum radius module, and as long as you haven't exceeded the practical values for the superelevation or for the side-friction factor, you know that your design is acceptable . You will probably need to test several different curve radii before you select your final design. While iterating, you also need to consider other factors: the cost, environmental impacts, sight distances, and, of course, the aesthetic consequences of your curve. Most surveying books contain a complete chapter on the layout of horizontal curves, and consequently, we won't delve into the surveying issues. Please refer to your surveying texts for this information.
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