I dug up some rather old research on dangerous drivers summarised in a 2003 report for the Parliamentary Advisory Committee for Transport Safety (PACTS). I doubt if the patterns have changed much in the intervening years...
75% of dangerous driving offenders are males under the age of 30. 97% of those convicted of dangerous driving in 1999 were men and only 3% were women. 40% came from postcode areas in ACORN group F (the Striving category, incorporating council estates and multi-ethnic, low income areas), twice the proportion of the national population in these areas.
...being charged with dangerous driving was not usually the first or last driving offence for many of those involved. 46% had already been convicted on three or more previous occasions.
56% of offenders with 3 or more previous court appearances in 1996 committed a subsequent offence in 1997. 40% of drivers with previous offences had already committed an offence connected with insurance. Neither current penalties nor the threat of a prison sentence had a significant effect on re-offending rates.
The overlap between mainstream offenders and offending as a motorist has been neglected … serious traffic offenders are more criminal, in terms of non-motoring convictions, than the population as a whole … traffic offending and mainstream offending are both manifestations of the same tendency to deviance...those repeatedly committing serious traffic offences are likely to commit mainstream offences as well. The evidence shows that serious traffic offenders cannot be thought of as otherwise law-abiding members of society... 50% of dangerous drivers had a previous conviction and 30% had a conviction for car theft.
We're simple folk here at Cycalogical, so I'll summarize the above in four words: "don't let criminals drive."
Perhaps part of the criminal justice system should involve assessing whether a convicted criminal can be trusted to drive, and much wider use of long driving bans as a punishment. I've pointed out before that a driving ban is a cheap punishment to administer; a lot cheaper than prison or community service. It also has the potential (based on the above research) to prevent dangerous driving and thus save lives.
Of course, banning someone from driving does not actually prevent them driving. Note above that 40% of dangerous drivers in the study referenced had insurance-related convictions (and it's likely that many of the other 60% had committed insurance-related offences but not been caught).
However, it is rather easier, given appropriate technology, to catch a driver for an insurance or license offence, because as soon as they get behind a car they commit the offence. With dangerous driving, you have to catch the offender in the act, which is very difficult to do given the fact that traffic police are on the endangered species list.