In the case of rail workers, there is a separate retirement system just for rail workers. Everyone else has a retirement system called "Social Security." If you have earned a retirement benefit (well, it is an annuity) with the railway worker plan, quit to work in a job covered by social security, it is possible to lose your railway annuity. This is why many of the rail workers "don't just quit". Additionally, there are anti "double dipping" laws that reduce your railroad annuity if you get social security.