I always get stuck in the roundabouts! 
The diamond intersection definitely looks intriguing. I wonder though, are they really that much more efficient? I mean if it's my understanding you still have to wait through traffic lights.
Yes, you
might still have to wait for traffic lights. But it is a safer, more efficient design. In the example below (I-44 and Kansas), you see that right turners entering the interstate do not pass through a traffic light and yield to left-turning traffic (just like they do with a standard diamond interchange)
If you do need to make a left turn to get on the Interstate, you must pass through one traffic signal (instead of two) and proceed through the interchange and use the "left turn bay" just before you hit the second signal. The benefit of this design is that left turners do not have to stop at the second signal, as there is no oncoming traffic to deal with, which is a safety issue. The only traffic that must pass through both signals are the cars that are going straight through the whole thing to Bolivar or Springfield.
People turning left
exiting the Interstate will yield instead of stopping, as they do with a standard interchange. This design is better here too, as left turners do not have to cross two lanes of traffic to get on the road, as they would in a Standard Diamond, another safety issue. Right turners exiting the Interstate might stop at a signal, but it is as easy to make a right turn with a DD Interchange as it would be with a standard one.
DD Interchange
Standard Interchange
The biggest downside is the learning curve, getting people used to this new design. Once we get past that, it is awesome.
