# Safe speed for horizontal curve

Calculate the Safe speed for horizontal curve with our free online tool using the input parameters: Radius, Superelevation

Use this calculator to determine the maximum speed at which a vehicle can safely navigate a horizontal curve. Cornering force, also known as side force, is the lateral force exerted by the vehicle while turning. By inputting the specified speed limits, such as 50 mph, this calculator will provide you with the corresponding safe speed limits for horizontal curves, ensuring optimal safety and control.

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Superelevation
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If the safe speed of a horizontal curve exceeds 50 mph

\text{Safe Speed for Horizontal curve ( V > 50mph )} = \frac{{-0.03 \times r + \sqrt{{0.03 \times r \times 0.03 \times r + 4 \times r \times (15 \times \left(\frac{e}{100}\right) + 3.6)}}}}{2}

If the safe speed of a horizontal curve is less than 50 mph

\text{Safe Speed for Horizontal curve ( V < 50mph )} = \frac{{-0.015 \times \text{r} + \sqrt{{0.015 \times \text{r} \times 0.015 \times \text{r} + 4 \times \text{r} \times (15 \times \left(\frac{\text{e}}{100}\right) + 2.85)}}}}{2}

The variables used in the formula are:

r = Radius of Horizontal Curve(ft)

e = Superelevation

When driving on curved roads, you may notice that the outer side of the curve is slightly raised compared to the inner side. This is done to counteract the vehicle’s tendency to move outward due to the center of gravity. It’s known as superelevation. With the knowledge of the curve’s radius and superelevation, you can determine the safe speed limit using this calculator designed specifically for horizontal curves. It ensures that you can drive within the appropriate speed range for a given curve, promoting safety and stability.