Totally hell no on highways ! , however these damn things beat stop signs on one street and nothing on the other at an intersection , AS LONG AS the circle is only ONE lane wide.
Hell no, especially not on state highways!!! Washigton state has lost their damn minds with these stupid things!!
Edit: Idaho is starting to do it too... It has made traffic worse every where they put them because people lack the common sense and/or curtesy to use them the way they are supposed to be used.