What type of track surface will least likely cause a train to skid when coming to a stop from 30 MPH?

The type of track surface that is well polished and dry provides the best traction for a train coming to a stop from a speed of 30 MPH. This is largely due to the friction generated between the train's wheels and the dry surface, which allows for more effective braking and minimizes the risk of a skid.

When rails are polished and dry, they typically have a smoother texture that facilitates better contact with the train's wheels, enhancing the braking performance. The ability to brake effectively is crucial in preventing skidding, as sufficient friction is required for the brakes to function efficiently.

In comparison, surfaces that are wet and slippery, rough and uneven, or snowy and icy all significantly reduce the friction needed for effective braking, increasing the likelihood of skidding. Wet surfaces can lead to hydroplaning effects, while rough surfaces can result in unpredictable stopping distances. Snow and ice create extremely low-friction conditions, making it very difficult for trains to stop safely in a controlled manner.