The Office of the Labor Member US railroad Retirement Board has released their monthly Questions and Answers for our benefit. The May 2018 topic is Railroad Retirement Age Reductions.
Railroad retirement benefits are subject to reduction if an employee with less than 30 years of service retires before attaining full retirement age. While employees with less than 30 years of service may still retire at age 62, the age at which full retirement benefits are payable has been gradually increasing since the year 2000, the same as for social security.
RRB May Publication
Link to RRB Questions and Answers