$1 billion -- That's the estimated sum a widespread disability scheme among Long Island Rail Road retirees could have cost the federal Railroad Retirement Board if the fraud hadn't been uncovered.

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After a federal probe, the board cut benefits for 600 LIRR retirees who were certified as disabled by a Garden City doctor who later pleaded guilty to conspiracy.

Now the LIRR wants to revoke their pensions as well. Workers who are truly disabled can reapply for disability benefits -- a hassle, probably, but a crucial step to whittle out those who committed fraud.