I can't quite get my head round what you are picturing Raggytash.
Do you picture moving one bicycle plus one person(~80kg?) five miles
creates only slightly less CO2 than
moving one car plus one person(~800kg?) five miles?
I'm picturing it as burning
about four digestive biscuits(200kcal)
v
0.3 litres of petrol(3,000kcal)