Welcome Tom.
I think we'd all be interested in your trip to Singapore, should you have the time to tell us (please?!
)
Having only 'just' passed 'O' level maths, I'm afraid that I can't help much with your questions. I do think (from what I've read), that rail travel is the most efficient form of mass transit regarding the carbon footprint versus people/goods actually moved.....but I'm prepared to be told that I'm wrong!