Speed is a contributory factor but it is poor driving skills that is the prime culprit.
As all motorcyclists will tell you - failure to achieve and maintain the national speed limit during your test (which must include dual carriageway) will result in failure as this is deemed to display inability to control your vehicle adequately.
The way to reduce death on the road is to improve driver training, including the use of skid pan training and possibly introduce re-training/licencing. At least that way the old boy of 67 who learnt to drive when people walked in front of their vehicles with a red flag would be cpable of dealing with modern traffic.