So, assuming it hasn't changed much in the past 15 years, the road that is closed (the A4085 according to news reports) I know it well. It's fairly narrow, at the side of the road there are ditches, streams and at least one river. The road goes quite close to the river in some areas and in particular there is a sharp bend and a bridge across the river at one point. Additionally, in places the sides of the road are heavily wooded, although I'm not sure what type of trees so at this time of year it's possible that the trees have no leaves. I think a vehicle could come off the road at any of several spots along the road and not be seen easily. It's a beautiful area, very picturesque but a challenging drive in bad weather.