Yup, dumbbell or teardrop junctions would work:

https://goo.gl/maps/ubJzB9XFvsy
https://goo.gl/maps/D8T1vzwWQCN2

although the latter isn't so good for HGVs. But at least you don't end up with utter disasters of junctions like this:

https://goo.gl/maps/rjfVX8fg6CE2

Just... Why? One of the roundabouts and one of the grade junctions are signal controlled as well, too, just to make sure the A421 gets nice and backed up.