There are three offences of dangerous driving - causing death by dangerous driving, dangerous driving and careless and inconsiderate driving.
According to current legislation, a driver is guilty of dangerous driving in one of two ways.
Firstly, the way he or she drives falls far below what would be expected of a competent and careful driver, and secondly it would be obvious to a competent and careful driver that driving in that way would be dangerous.
And driving without reasonable consideration for other road users. The evidence must show that other road users were inconvenienced by the inconsiderate driving of the defendant.
Speeding, using a mobile phone, reading a map, eating, drink-driving, plus many others incidents, could all be considered as dangerous and/or careless driving.
What are the penalties?
The maximum penalty for causing death by dangerous driving is a 14-year jail term.
Other options include an unlimited fine, a minimum two-year driving disqualification and penalty points.
For dangerous driving, the maximum prison term a court is allowed to prescribe is two years, while it can hand out an unlimited fine, a disqualification and penalty points.
For careless and inconsiderate driving there is a £2,500 maximum fine (the government currently wants to raise this to £5,000). Disqualification is at the court's discretion and it can impose penalty points.
The penalty for refusing to provide a specimen of breath, blood or urine for analysis is a maximum 6 months' imprisonment, up to a £5,000 fine and a driving ban of at least 12 months.
Where a court disqualifies a convicted driver, it must order an extended re-test - about twice as long as the ordinary driving test.
The courts also have discretion to order a re-test for any other offence which carries penalty points.
Who is driving dangerously?
In 2004, 10,276 drivers were prosecuted for dangerous driving, of which 4,467 were convicted. There were 40,858 careless driving cases - 30,102 were found guilty.
Of the 107,091 taken to court for consuming alcohol or drugs, 95,521 were convicted.
A report for the Department of Transport examined nearly 6,000 accident case files.
It found that in 44% of fatal accidents, the driver at fault was killed and in 20% of cases a pedestrian at fault was killed.
Of the remainder, 10% of drivers were reported for causing death by dangerous driving and in 20% of cases a driver was reported for careless driving.
The remaining 6% were cases where the driver was reported for other offences.
It also found that those convicted of dangerous driving were mainly young males - for example, in 1996, 75% of the dangerous drivers were men under 30.
How prevalent is drink-driving?
Between 1979 and 1994 drink-drive accidents fell from just under 20,000 to less than 10,000.
Since then the number has risen to 13,000.
In 2002, nearly one in six of all deaths on the road involved drivers who were over the legal alcohol limit.
People who drive at twice the current legal alcohol level are at least 50 times more likely to be involved in a fatal car crash.
What is the drink-drive limit?
The legal limit in the UK is 80 milligrammes of alcohol in 100 millilitres of blood, but there is no failsafe guide as to how much you can drink and stay under the limit.
How much alcohol is in your blood can depend on many factors such as the amount and type of alcoholic drink, your weight, sex, age, food intake and metabolism.
More than half a million breath tests are carried out each year and on average 100,000 are found to be positive.