[BozoTexino]

Mythbusters did a test on their show on roundabouts vs. stop signs. Roundabouts were more efficient.

[Alberta's Child]

It’s almost intuitive that a roundabout would be more efficient than a stop-controlled intersection. At a stop sign, every motorist must stop even if there isn’t another human being within a hundred miles in a car or on foot. At a roundabout, an approaching vehicle must slow down but doesn’t have to stop unless he is approaching a yield sign and another vehicle has the right of way.

[Alberta's Child]

Here’s something else most non-professionals may not know:

When traffic volumes are high, a partial cloverleaf interchange with two traffic signals on the minor crossroad will operate more efficiently than a full cloverleaf with no traffic signals that is designed to accommodate “free flowing” traffic.