EVERY single driver involved in an accident in Oxfordshire this month will be asked to take a breath test.

Extra patrols will also be carried out across the county at all times of day.

The crack-down is part of Thames Valley Police's annual Christmas anti-drink-driving campaign, Operation Holly.

In particular, the force has warned people to think very carefully about the morning after.

Officers have said that after just four pints of lager, the average adult may not be safe to drive for up to 13 hours.

That means if you finished drinking at 11pm and went home, you could still be over the limit at midday the next day.

Online calculators to work out when you might be safe to drive - like this one -  allow one hour for each unit of alcohol, plus an additional hour for the first drink to allow for the alcohol to enter the bloodstream.

It then rounds up the calculation to the nearest half hour.

The calculator bases its calculation from the time you stop, not when you start drinking. 

Police have has also warned all drivers who occasionally take drugs that there will also be drug testing, and that just a trace amount in a person's system could lose them their licence.

Thames Valley Police has also called on good citizens to 'shop' careless road users who they suspect might be over the limit or on drugs.

Road Safety Sergeant Chris Appleby said: "Drug and drink driving are both very serious offences and all drivers need to understand the gravity and consequences of their actions if they drink and drive. If you are not sure, then it is not worth the risk."

"Operation Holly is designed to be a deterrent to any motorist thinking about driving while impaired by the effects of drugs or alcohol. The importance of personal responsibility for your choices must be emphasised.

"Please think about the pain and misery you could inflict on innocent road users by a reckless decision to drive or ride after taking drugs or consuming alcohol.

"Drug drivers should realise we can now test on the roadside for certain drugs. Only a trace amount of an illegal drug in a person's system could lose them their licence like drink driving. We do not need to prove you are impaired."