These two signs on I-93 at Exit 15 in Concord have different patterns of reflective materials, and were placed to study which works better. The sign at left has one coating for the background and a different coating for the letters. The sign at right has the same coating on both background and letters, which makes the words harder to distinguish at night. The left sign is now the state standard. (  DAVID BROOKS / Monitor staff) - Concord Monitor

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