Operationally three lanes can carry as much traffic as four in most cases due to left turns blocking traffic for those in the center lanes of four lane roads. At above 20k vehicles per day is where you start to have issues. By having a center turn lane instead of two through lanes you reduce rear end accidents considerably and make the road much safer for users. It is not a PR stunt. It is engineering [[safer) and economics [[less injuries and property damage) driving these road diets. http://www.walkable.org/assets/downloads/roaddiets.pdf
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