I disagree with that Scummymummy. As it stands at present, only a small minority of people face a disincentive to drive short distances (i.e. those who live on the border who face paying £8.00 to drive say 1 mile). If you live in the zone, you can obviously drive all day to your hearts content for a mere 80p (and by definition, these are London's wealthiest residents). Alternatively, if you are driving across London, the £8.00 charge is roughly comparable to public transport costs if there are 2 or more in the car. Also, once you've paid the charge for the day, there's no incentive to use other forms of transport than the car for that day.
Would people really be willing to pay £2 - £3.00 daily for a trip which could easily be done by bus or on foot? I personally don't think so.
As to my friends, their learning difficulties are certainly not extreme but what it does mean is that they go to a different school to their sister which combined with working parents means they can't fit public transport into their morning schedule given allt he logistics.