We scrutinised 11 million car insurance quotes run on our site in the 12 months to September 30 to identify the biggest offending postcodes for driving under the influence.

Crewe (postcode CW) took first place, having logged 1.74 drink or drug-driving convictions per 1,000 drivers.

The next four slots in the top five are occupied by Welsh postcodes – Llandrindod Wells (LD – 1.60 per 1,000 drivers), Cardiff (CF – 1.59), Newport (NP – 1.58) and Swansea (SA – 1.58).

At the other end of the scale, the three postcodes with the lowest number of convictions per 1,000 drivers are in London (WC, NW, and E). London WC had a conviction rate of just 0.12 per 1,000 drivers, with NW at 0.66 and E at 0.68.

The other two postcodes in the bottom five are Bradford (BD – 0.68) in Yorkshire and Ilford (IG – 0.76) in Essex.

Improving situation

The good news is that the overall number of convictions for drink and drug-driving appears to be in decline.

The highest rate of offences when we ran these numbers last year was 1.98 per 1,000 drivers – this was in the Llandrindod Wells postcode. That means we’ve seen a drop of some 12% in the 12 months to October 2015.

Similarly, the lowest rate of convictions in 2014 was 0.76 in the London E postcode, but this tumbled to 0.12 in London WC this year.

Party season

While this is encouraging, drink and drug-driving remains a significant problem on UK roads, with an estimated 100,000 convictions every year. According to the Department for Transport, drink-driving incidents are responsible for around 500 deaths and 2,500 serious injuries every year.

The peak time for drink-driving is the summer, reflecting the fact more people drive to pubs in the evenings. But, perhaps inevitably, there is another spike in the weeks running up to Christmas and New Year.

Social pressure

For most people, drink-driving has long been socially unacceptable, but there are clearly people still getting behind the wheel while intoxicated.

Some of these will know they’re over the limit but will still take the risk and hope they’re not caught. But in other cases, drivers who would never dream of driving under the influence are being convicted when they think they are sober.

An example could be someone who has a few drinks at a Christmas lunch and then takes the train home. They might think they’re fine to drive home from the station but, in fact, they could still be over the limit.

The same applies the morning after an evening’s drinking. Alcohol lingers in the body for many hours, so even someone who has consumed a relatively modest amount could find themselves at risk of conviction the next day.

The general consensus is that the body processes alcohol at the rate of one unit per hour. If a pint of lager has three units, someone who drinks three pints in the hours up to midnight could still be over the limit when driving to work or doing the school run the next morning.

And it’s worth remembering that no amount of sleep, coffee or showers will make you sober up more quickly. Time is the only way to make you legal to drive.

If you’re convicted…

There are serious consequences for those caught for drink or drug-driving, including:

- a jail sentence of up to six months,
- a driving ban of at least a year, and
- a fine of up to £5,000.

You’ll also have a criminal record. And even after a punishment has been served, a conviction will sit on your licence for 11 years and you’ll have to declare the offence when you apply for car insurance for five years.

Offending drivers typically see their premiums shoot up by around £350, which is more than the cost of some people’s policies in the first place.

So the message is clear and simple: if you’re going to drink, don’t drive. And if you’ve had a drink, give your body enough time to get rid of the alcohol.

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