It is an NHS supply station for ambulances. Given the confusion by making part of the road structure two way and part one way (unless you are suggesting St. Davids be two way, I hope not, way too narrow) I would expect to see a number of accidents in fairly short order.
The issue is not caused by 99.9% of drivers, just those idiots who DGAF (Google for definition, it's a bit fruity for here ).