A train needs friction between its wheels and the rail's upper surface in order to move, but friction between the wheel and the sides of the rails is a different matter. Over time, the stress from this friction, especially as trains go around curves, can cause rails to crack; sometimes train wheels even climb over the sides of tracks and derail. The railroad industry combats this problem by applying lubricant to rails, but it's far from a perfect solution: The environmentally unfriendly stuff seeps into the ground and sometimes spreads to the rail tops, making them slippery. Researchers at Argonne National Laboratory in Argonne, Ill., are using a laser to rapidly melt and re-solidify the steel on the side of the rail. This "glazing "creates a slippery surface that is also more durable. Although research is still in its early stages, principal investigator Ron DiMelfi estimates that laser glazing could save the U.S. railroad industry $40 million per year on fuel and $16 million per year on rail replacements.

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