Making U-turns is not legal in which of the following areas?

Making a U-turn at a rail crossing is illegal because it poses a significant safety risk. Rail crossings are areas where vehicles might encounter trains, which can often approach quickly and unexpectedly. Making a U-turn in such a location could lead to a vehicle being stuck on the tracks or obstructing the pathway of an oncoming train, resulting in potentially catastrophic consequences.

In contrast, while a U-turn might not be advisable in other locations like highways, the crest of a hill, or in a curve due to visibility and safety concerns, these areas do not carry the same specific legal prohibition as rail crossings do. Thus, U-turns are explicitly forbidden at rail crossings to ensure the safety of all road users.