Tom Vanderbilt summarizes urban planning efforts to update the intersection:
Left turns are the bane of traffic engineers. Their idea of utopia runs clockwise. (UPS' routing software
famously has drivers turn right whenever possible, to save money and time.) The left-turning vehicle presents not only the aforementioned safety hazard, but a coagulation in the smooth flow of traffic. It's either a car stopped in an active traffic lane, waiting to turn; or, even worse, it's cars in a dedicated left-turn lane that, when traffic is heavy enough, requires its own "dedicated signal phase," lengthening the delay for through traffic as well as cross traffic. And when traffic volumes really increase, as in the junction of two suburban arterials, multiple left-turn lanes are required, costing even more in space and money.
The diverging diamond interchange (above) engineers left turns out of existence but may not be able to keep up with higher and higher traffic volumes.
The Dish 