What equation should be used to check the maximum train speed on a curve with a 3 degree curve and 2-1/4" superelevation?

The maximum train speed on a curve is determined by taking into account both the curvature of the track and the superelevation provided. Given the context of a 3 degree curve and a superelevation of 2-1/4", the appropriate formula to use is the maximum speed equation, especially one that fits the parameters of the curve and superelevation.

Using the Vmax equation allows for an accurate calculation by analyzing how much lateral acceleration a train can safely handle when navigating a curve. The equation factors in both the radius of the curve, which is defined by the degree of curvature, and the amount of cant or superelevation, which serves to counteract the centrifugal force acting on the train.

The other choices involve either minimum speed or less relevant curves or safety formulas that do not specifically address the criteria needed for determining maximum speed in this context. Therefore, the Vmax equation effectively ensures that the calculations align with the specific conditions of curve and superelevation, resulting in a safely determined maximum train speed.