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So the very first result on Google for "double decker fuel efficiency" give the result "per gallon, while a 'double-decker' bus with a Diesel engine will run 11 miles per gallon".

44 / 5 days is approx 9 miles poet day. 4.5 miles to and 4.5 miles back.

I didn't want to believe this but I guess city dwellers where double deckers operate would probably have short commutes like this on average