I done my skills test in Florida, when i was told i had an engine failure I was asked where am I going to land. I said "the huge interstate below me"
It seemed enough to satisfy the examiner.
At the end of the day I guess it depends on the terrain around you. And time of year. For instance I would not fancy landing on a field in the middle of the wet season, harvest time, or plough the field ready for planting time. But then again UK motorways are always bumber to bumper. And tiny roads have power line for phones strung accross them.