They roll merrily along the nation's railway system, hazardous chemicals and high explosive on wheels. They are the thousands of aging, flawed, and defective railroad tank cars in use today.

Through a fluke in federal law made worse by a regulatory agency's foot dragging, thousands of privately-owned, known defective railway tank cars are daily filled with acids, flammable liquids, gases, and other dangerous chemicals. They are sent, unchecked and unsafe, onto the nation's railway system where they are vulnerable to accidents, punctures, leaks, and ruptures.The accident record is terrible and getting worse as the cars age. Railroad tank car accidents are responsible for some of the most massive and disruptive urban evacuations in the nation. The largest occurred in July 1986 in Miamisburg, Ohio, when three tank cars in a derailment ruptured and caught fire. The toxic smoke cleared 30,000 people from their homes; 569 were treated for exposure to it.

The Federal Railroad Administration (FRA) is the agency charged with setting and enforcing tank car safety standards. But the FRA has allowed compliance with safety standards on cars built before 1971 to be voluntary.

Further, the FRA has turned over monitoring that voluntary compliance to a committee made up of representatives from the railroads, chemical companies that own the cars, and tank car manufacturers.

From one perspective the railroads are not to blame. Railroads own very few tank cars built before 1971. The majority of the 200,000 in service now are owned by chemical companies. And, under federal law, if the cars meet current safety standards or were built before the standards went into effect, the railroads cannot refuse to haul them.

From another view, the railroads must share the blame. Improper handling of the cars, poor track maintenance, and lax safety standards contribute to the derailments that cause many of the accidents.

But the majority of the blame must be laid at the doorstep of the FRA, the regulatory agency which has ducked the issue. The FRA has backed off requiring tank cars manufactured before 1971 to be modified to current standards, making it voluntary instead.

Something can be done, as was demonstrated by Canada after the 1986 Ohio incident. The Canadian Transport Commission ordered all tank cars with defects similar to the ones in the Ohio accident off their nation's rails. Period. No foot dragging, no lobbying to block a clear order: Meet the safety standards or park it.

It's a solution that ought to be applied here.