Before the “Jingle Bells,” “Silver Bells,” “Carol of the Bells” and “Come on, Ring Those Bells” again become out of season, it would be wise to prepare ahead of the worst of the 2012 holiday traffic. Think of the city streets during Christmas season as a fat-clogged heart, where road users are like blood flowing to and from the diseased organ. Where the arteries have been clogged with fatty cholesterol after years and years of eating pork, beef, chicken and other LDL-laden foods, normal blood flow is slowed down and, at worst, grinds to a complete stop. Now that’s another set of bells tolling. The same logic can be applied to traffic: Lifetimes of selfish habits have led to chaotic road conditions on urban streets, and try as they might, our heroic traffic enforcers are rendered powerless by a problem that has become systemic.