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Published on September 4, 2006

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Date Published September 4, 2006
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Recent research has shown the nominal legal minimum tread-depth requirement of 2/32 of an inch (1.6 mm) for passenger car tires is inadequate for wet-road traction at highway speeds. Significant reduction in available friction occurs when tread depths fall below 4/32 of an inch (3.2 mm), even for minimally wet roads, and well before hydroplaning begins. No rational basis in highway safety has been found for the present requirement.