Research by the Institute of Advanced Motorists has shown that drivers who commit serious offences are getting off more lightly then they did 10 years ago.

Fifty-three per cent of those convicted of causing death or bodily harm through driving offences were sentenced to immediate custody (260 people) in 2011. This has dropped from the 83 per cent sentenced to immediate custody in 2001.

The average sentence for causing death by dangerous driving is just four years – 62 per cent shorter than for manslaughter. The average sentence length for manslaughter is 6.6 years. Those sentenced to prison for causing death by careless or inconsiderate driving are given an average sentence of 1.3 years. Causing death by careless driving when under the influence of drink or drugs carries an average sentence of 4.35 years.

Fines for drink driving are also lower in real terms than they were ten years ago. In 2001 the average fine for drink driving was £203 – the average £240 fine in 2011 was equivalent to just £178 in 2001 prices – a 12.3 per cent decrease.

The average fine for careless driving is £138, 27 per cent less in real terms than it was in 2001. Dangerous driving is the only area with tougher fines. The average fine is £518 – 30 per cent more in real terms than in 2001.

IAM chief executive Simon Best said: "We recently discovered that the number of prosecutions for motoring offences have fallen. Now it is clear that drivers are also receiving short sentences for some of the most serious driving offences."

This is rather depressing news. It took years to get the law changed to create the offence of causing death by careless driving. The earlier offence of causing death by reckless driving had been almost unenforceable, because recklessness implied a wanton disregard for safety that was very difficult to prove. Now we have correctly worded offences, but the IAM argues the custodial sentences do not fit the crimes.