[xoxoxoBruce]

London startup, the Hummingbird Bike Company has designed a folding carbon-fibre bike that weighs just 6.5 kilograms. The company claims the cycle is the "world's lightest folding bike", weighing three kilograms less than its competitors – the equivalent of four pineapples, and less than the average watermelon.
Craciun designed the first Hummingbird after becoming frustrated with the lack of affordable options for bikes that can be folded down to fit into elevators, or be easily carried upstairs.

looks strictly urban in nature to me, and carrying upstairs and in elevators you still have the problem of dirty tires touching anything, especially fellow elevator riders.