KneesUp
Guru
I suspect it's based on averages, and works when you look at the whole picture. Obviously individual cases may vary,.That's all very vague and smacks of the nonsense on BBC4 I heard this week.
"Commuting for four weeks" means nothing. How far is your commute? Commute by what?
"half the carbon footpring of a car is in its manufacture". More vague. If a car does 500 000kms before getting scrapped, it's carbon footprint from fuel is higher than one that crashed when it left the forecourt..
(but it might correlate too - I'm poor/tight so I have an older, higher mileage car (10 years old, 125k miles) and an older bike (30 this year, mileage unknown) I suspect people who cycle and own a newer car that they change regularly are also statistically more likely to have a newer bike they change more often too - although I fully accept that following this post there will be lots of posts about driving a 4o year old Land Rover that's been in perpetual motion since the war, but owning a brand new bike, as well as posts about driving a brand new car and riding the bike their grandfather used for getting to work)