Sometime in 1986 a retired railroad worker is going to walk to his mailbox and discover his monthly check from the Railroad Retirement Board is not there - and may never be there.

Unless somebody does something soon, the Railroad Board, which has existed to pay age and disability benefits to retired railroad employes and their families, will go belly up - it will ran out of money by 1986.

The tale of the Railroad Retirement System is a grim one of a country, an industry and a Congress that didn't know when to stop. It is a case study in how to let another government good will gesture get completely out of hand.

It all began in 1935 when railroad employment was removed from cover-age under the Social Security Act because the new federal pension payments weren't due to begin until 1942, and the nation felt that retired railroad workers deserved benefits immediately, and the industry itself was in bad shape.

To a great extent the Railraod Retirement Act grew out of a confrontation forced between rail management and labor by President Frankin Roosevelt.

From the outset, the system was designed as a contributory one, paid for equally by employes and employers.

But several amendments to the original plan significantly increased its benefits without significantly increasing the funding.

The first set of major amendments came in 1946 and 1951. In 1945, the plan was amended to include survivor benefits not unlike those provided for in Social Security, but about 25 percent higher.

Ammities based on occupational disability also were established in 1946 - astaff retirement feature. Under new provisions, it was recognized that someone not totally disabled could still be prevented from making a living because they could not do their regular job.

But another tradition began in 1946 as well, the first coordination between the railroad retirement system and Social Security. Responsibility for individual survivor benefits would be split between the two systems.

In 1951, the final addition of beneficiaries was completed for wives and dependent husbands of retired workers.

More significant, perhaps, was the fact that in 1951 a "financial interchange" between Social Security and the rail plan was finalized, with the railroad plan paying Social Security what it would have received from retired roalroaders had they been in the Social Security system, and Social Security paying the railroad plan the equivalent sum that its members would have earned under Social Security.

In recent years, that arrangement has resulted in 60 percent of the benefits of the railroad plan having been paidfor by the Social Security system.

Still, more and more benefits during the 1960s were added with fewer concurrent increases in income to the plan.

And, at the same time, the number of beneficiaries was increasing while the number of employes paying into the plan was decreasing.

Part of the problem of increasing benefits was the result of the enormous power of the railroad labor unions on the Hill. Since all amendments or changes in the retirement plan had to be approved first by management and labor, and then approved by Congress, union lobbyists were able to get Congress to sweeten the deal for labor after an agreement had been reached.

But in 1972, William Dempsey, then the head negotiator for the railroad industry - now its president - secured a major concession from the unions. They would no longer go to the Hill unilaterally. Whatever went to the Hill would be the final agreement between labor and management.

For that concession, the unions didn't actually get much in the way of money, but fringe benefits soared. One key provision allowed people to retire at age 60 after 30 years of service and receive a pension as if they had worked to age 65, which included supplemental ansulties and spouse anxities.

Another significant jump came in the area of benefits received by widows and other survivors. While most of those beneficiaries received benefit amounting to 110 percent of what would have been paid had the worker been covered under Social Security, the new agreement hiked that to 130 percent.

But the 1974 agreement also contained other significant revisions in the program. Because of certain escalator clauses in the system, it actually was possible that benefits could exceed full pay at some point down the line.

By 1974, the cost to the railroad industry of dual benefits - payments to retirees from both the rail plan and Social Security - exceeded $450 million per year, and promised to be a major reasonable fund would go best by the 1980s.

The problem was that any benefits paid by Social Security to a railroad beneficiary have been deducted from the benefit amounts calculated under the interchange program. In other words, it was money that would have gone to the rail program had it not gone to one of the retirees.

By 1974, the camulative loss to the rail system in payments made by Social Security directly to railroad pensioners had totalled $4 billion.

Because of the critical nature of the dual benefits system, management anelabor agreed to phase out such benefits by the end of 1974, unless the employe in question was vested, had 10 years of railroad service on changeover, and had spent enough time in the Social Security system to be entitled to a benefit at age 62. Such payments became known as the dual benefit "windfall."

In any case the government now is involved totally in attempting to save the railroad system, making huge yearly payments under provisions of the Railroad Retirement Act of 1974. That act provides for the government's general fund to make appropriations to the railfund for the next 25 years in an effort to phase out higher returns resulting from dual benefits.

But the $250 million annual payment provided for in 1974 is already not enough, according to a report of the actuary of the plan, who said the annual payment from the Treasury will have to jump to $350 for each of the next three years. The financial deficiency of the fund, it seems, was underestimated considerably, according to the actuary's report two months ago. Instead of the deficiency being 1 percent of taxable payroll, it apparently is closer to 3.6 percent.

"There are only three possible ways to take corrective action," the report states. "Reduce benefits, raise taxes and get a subsidy."

One federal regulator said the government has three choices of its own. "We could tell the system to just take what it has and spread it around to everyone, severely cutting back benefits," he said. "Or we can tell them what to do, or we can fold the entire system into Social Security."

But the fact remains that altough things are better for the fund now than they have been in the past, "further corrective action is needed," according to the actuary, who admits that withoutsomething done soon, "the account will run out of money and be unable to pay benefits sometime before 1980."