There was a very similar discussion here, although it was quite a long time ago. It went on for a very long time and got quite heated! One of the conclusions, though, was that it would vary certainly depending on the country, and possible the area within the country, particularly with regard to the road option.
For example, the the US there are many very long, straight roads which maybe see a couple of cars a day - they would be good landing sites. On the other hand, the M25 wouldn't. Since the original poster specified the UK, I'd suggest that a road isn't an option - in those parts of the UK where roads are quiet enough to consider, they're usually not straight enough to be worth considering.
FFF
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