Rail Europe does not impose a specific age restriction for traveling alone on its trains. However, the policies regarding minors can vary depending on the individual train operator and country. Generally, children under the age of sixteen might be required to travel with an adult, but this can differ based on the service. It is important for parents or guardians to check the specific regulations that apply to the train they plan to take. Additionally, it is advisable to consider the child's comfort level and ability to navigate train travel independently. For the most accurate information and any specific age-related policies, you may want to refer to the current web page that outlines the rules and recommendations provided by Rail Europe. It is always best to be well-informed before embarking on travel, especially for younger travelers.