The phenomenon of young people driving less than previous generations is becoming more and more well known. The concept has been dubbed "peak car" and occurs in many developed countries, not just the UK. Per capita driving in the UK peaked around 10 years ago, whereas train use and public transport use in London and certain other cities has increased dramatically.
The theory is that young people are less interested in cars and acquiring driving licences as they are considered "old tech". They would rather get an iPhone than pay for driving lessons. Young people also prefer to live in urban areas where car use is less useful. A lot of young professionals now live in city centre apartments where car use is a big hassle.
It's not just that the number of miles per car has peaked but the average numbers of cars per household has flatlined and the total number of miles driven as a nation as fallen since the peak in 2008 and is slightly less than that seen in 2003.
The Dft publish traffic growth rates for where they think traffic volumes will be going forward, these have been lower than the low range given for the 1989, 1997, 2008 and 2011 figures, which each subsequent prediction setting the growth rate lower than the previous versions. That means that road traffic is lower now than it was expected to be in 2000 by the 1989 model.
Part of it is people are realising that for many people (excluding purchase costs and before driving a single mile) a car can easily cost £500 (for a very cheap to insure car, with low car tax and low maintenance costs) and for most will be closer to £1,000 (£100 tax, £200 service and MOT and £700 insurance). Add to that the purchase costs (which can easily be another £1,000 a year, or for an older cheaper car it often then pushes up the maintenance costs resulting in the same overall figure) and that is quite a few uses of a car club car, taxi journeys and train or bus tickets before fuel start to come into play.
Of course there are other "costs" with owning a car such as needing somewhere to park it at or near home (either in the form of the cost of a house with a drive, garage or some other space, alternatively needing to have a residential parking permit) and/or needing to park it at/or near work (car park charges).