In December, 1968, the Silver Bridge across the Ohio River at Point Pleasant, W.Va., collapsed under a load of bumper-to-bumper traffic. Forty-six people were killed, and the dangers of old, under-inspected bridges suddenly became a national concern. The inevitable result was a federal standard, ordered by Congress, that required every state to inspect every bridge on a public road at least once every two years.

That requirement, state highway officials have been telling the Federal Highway Administration, is a little too rigid and does not take the experience factor into account. Why, they ask, should a brand-new bridge be examined every two years? Why not every every four? On the other hand, there are bridges that should be inspected every few months because experience has shown that they need it.

Thus FHWA, in a proposed new rule, says it has made the "tentative determination that the inspection interval can be increased for some categories of bridges with only a minimal or negligible increase in risk to the public." It proposes that states be permitted to extend inspection intervals for those kinds of bridges and use their bridge inspectors more efficiently. The public comment period will remain open until March 21.