It is routes such as ring roads where effectively it is a crossroads with one of the crosses being 4-6 lanes wide at 40mph and the other being 2 lanes approachi

It is routes such as ring roads where effectively it is a crossroads with one of the crosses being 4-6 lanes wide at 40mph and the other being 2 lanes approaching at 30mph, (though not always such a speed disparity). So if you arrive from the 2 lane 30mph road you could have a very long wait time.