are people more likely to ditch their car in one fell swoop or one step at a time?

If you enjoy a cheeky bar of chocolate with your coffee every evening, it's probably fair to say you've a habit that would be difficult to give up overnight.

Instant abstaining is difficult for most people so cutting down (only on weekdays etc) over time is a more realistic alternative.

Adapt either approach and if you can get through that first month, you'll find yourself healthier, slimmer and no doubt a few quid better off. Carry on your behaviour and before you know it, you've got yourself a new chocolate-free habit.

So your two approaches to behavioural change are taking everything away in one fell swoop and reducing it a little at a time.

Which one would be most effective for selling public transport?

Let's say you are a heavy car user who has never really considered bus travel as a viable alternative (a pretty decent chunk of the population?). Your local bus company is selling their services as the solution to problems you don't really think you have. 'Ditch your car forever' they say, 'Petrol is expensive' they say, and offer unlimited travel around the city for £4, free wifi and leather seats as a sweetener.

Now, are you more likely to say 'That sounds amazing. Take my car keys as I'm never, ever going to need them again' or perhaps something along the lines of 'Yep, you make some decent points. Realistically I can't give up my car totally but I'll definitely consider bus travel for some journeys in the future. Got any deals on?'. I know which one I'm siding with.

Of course, we have to sell the bus as a transport solution but expectations of an overnight holy grail shift have to be more realistic. If you want one travel habit to morph into another, taking things one step at a time is more likely to lead to long-term behavioural change.

Who's got the Mars bars?