On a weekend just have to avoid the road there. Yes it is busy but what makes it so awful is everyone slowing down to 20mph so they can gawk at it. Then there is the inevitable shunts as someone forgets to brake in a line of traffic. Personally I would plant a hedge to shield view from the road. This in itself will make traffic flow better. Of course hedge will just not fit in with the Salisbury plain landscape. Stonehenge was put there originally for its long views of the horizon and the sun rising/setting.