>>1278870I did seriously contemplate that at one point and I came up with an objective solution: air pollution levels.
The idea is that areas with beautiful scenery will tend to be out in the country away from populated areas and the pollution they cause. Hence, places with lower pollution would imply decent outdoor scenery, and areas with high pollution would imply oozing urban sore scenery. I found a suitable site with lots of data:
https://giovanni.gsfc.nasa.gov/giovanni/#. You can even create custom maps based on that data (pic related). It's an NO2 level map, which is a specific type of air pollutant that's heavier than air, which lingers in the atmosphere longer, and hence it's ideal for spotting polluting areas. The only minor flaw is that NO2 is also generated in low levels by lightning storms (hence the light blue areas on the map near the equator).
I ultimately decided not to include it, as natural scenery is not necessarily an indicator whether the rail line will be epic or crap. There are a lot of urban rail lines, such as the B&O Railroad Museum in Baltimore, or the Science & Industry Museum in Manchester, that are pretty amazing, and not being out in the country doesn't take anything away from the experience. There's also an unusual one in England that runs through a modern working steel mill and shares tracks with work trains pulling vats of molten steel. 100% man-made, and yet it's totally fascinating. Here's a video:
https://www.youtube.com/watch?v=cPnzgiAac-o 