Some pennies are better left unpinched.

That's why allowing far longer tractor-trailer rigs to ride on the Long Island Expressway and the nation's other interstate highways to cut costs for shippers and companies like FedEx and Amazon isn't a smart idea.

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The U.S. Senate is considering legislation, already passed in the House, that would allow trucks up to 84 feet long on interstate highways. That's two tandem 33-foot trailers riding behind the cab of a truck -- which is almost 10 feet longer than the current limit. Anyone who does much highway driving knows how scary the currently allowed 28-foot trailers are when they're doubled up. Many truck drivers weave in and out of lanes and pass with too little regard for vehicles around them. And anyone who drives on the LIE knows the density of traffic makes the trucks scarier, and the prospect of bigger rigs terrifying.

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Shippers say changing industry trends have them carrying mostly Internet shopping purchases, with loads far lighter than the 80,000-pound limit. They argue, with Republican support, that increasing truck lengths would cut costs. Democrats, led by Sen. Chuck Schumer, say the savings aren't worth the cost in safety and peace of mind.

Companies often have a blind spot when it comes to cutting expenses. Profit is their business. But the U.S. Department of Transportation's business is safety, and it has come out against the longer trucks, at least until further studies are done.

Congress ought to listen to the DOT.