The editorial "Drugs and Railroad Accidents" {Feb. 17} was on target. One scarcely knows how to react to the federal court decision that the Constitution protects drunken or drugged operators of trains from detection of abuse through federally mandated tests. Both laughter and tears are appropriate: laughter because of the wild improbability of the notion that the Constitution compels this sort of submersion of the public interest, and tears because, until this decision is reversed or suspended, countless individuals and communities will be exposed to needless risk.

The railroads have an excellent safety record and are extensively and effectively regulated by the Federal Railroad Administration. But as The Post pointed out, railroads are not immune from the drug and alcohol abuse problems that beset the rest of American industry.

Well, the unions have won this decision. Now let them defend it, both in the Supreme Court and in the court of public opinion. I am confident they will lose in both tribunals.

As to public opinion, consider only that, as The Post noted, it was because of the regulation struck down by the court that the use of drugs by the engineer of the freight train that slammed into a passenger train at Chase, Md. -- with a loss of 16 lives -- was discovered. As to Supreme Court review, it is heartening that several other circuit court decisions are flatly contrary to the Ninth Circuit's decision. If it is constitutional to impose drug tests on jockeys so that confidence in racing will not be undermined, as another federal appeals court has ruled, then surely it must be constitutional to test railroad employees responsible not for the well-being of gamblers, but for the safety of the public. WILLIAM H. DEMPSEY President, American Association of Railroads Washington