You lot are really missing the point with cars and how they are justified.
It isnt just down to comfort, cost, convenience and laziness the way cars are used in this country (and many others), by most sane reasoning some of the cars we buy and the journeys we do are fairly ludicrous, I see a neighbour get in a 70k Range Rover to go and get a paper (to be fair he walks his dogs miles every day) which is less than a half mile round trip, a seventy thousand (plus private plate) pound vehicle that weighs nearly three tonnes to take one average male half a mile to get a newspaper, to me, thats kind of back to front.
He can obviously afford it but nobody needs such a big expensive, powerful vehicle simply to get around, the cost of the newpaper, say a quid compared to the fuel, wear and tear, depriciation on such a vehicle for that half mile will be a lot more than that.
So, why do people do this, I think its human nature, a bit of amateur psychology would probably explain it, its like a point is being made, big cars are generally bought to show off a bit and its an opportunity to flex ones personal financial worth and ego, plus seeign as you are paying for it you may as well use it and no crime was committed as he is perfectly at liberty to do so, also driving a car like that is an enjoyable experience by and large, feeling of power, the comfort and the reassurance that you have one ok in life.
However, really, its unsustainable, the towns are gridlocked with massive (compared to the usual average sized owner even a Smart is huge) cars taking up a lot of space compared to the people in them, sat waiting, burning fuel, witness the third world contries moving thousands of people by bike and moped every day in crowded cities but we sit there hoping that people will see our true worth by the type of tin box we are sat in, dont get me wrong I am not above all this and am a bit of a car fiend but I can see it for what it is.
All these calculations are irrelevant, its the kind of thing people do in private but when they are out there sat in their mobile, leather lined, surround sounded, 300 hp chariot with knobs on the last thing they are thinking about is the cost, its whether that nice looking girl has checked out the wheels or whether other men are looking jealously at it, demoralise the male opposition and make the potential breeding partners see you would be a good bet, ok its a bit more complicated than that, some genuinely arent interested but a lot are so a push bike may cost nothing but it wont get you a shag ! (though the rippling body underneath may) not that cars do either but a lot think they might and every little helps.