Drivers have been warned to "prepare for the worst" as a potentially-lethal mix of black ice and frozen fog hits the UK once more.
The AA have issued a stark warning to all drives on UK roads, telling people to use "extreme caution" when driving over the weekend.
The AA said anyone heading out in the morning should add extra time and ensure the car is properly roadworthy as conditions were severe.
Spokesman Ian Crowder said on Thursday: "We have got the worst possible conditions really, of fog and icy roads, and that can be lethal.
"I think the message is extreme caution and to prepare for the worst and make sure all windows are clear."
The statement came as a weather warning from the Met office informed drivers to be wary of fog and sub-zero temperatures across England.
The Met Office said "freezing fog" had settled in patches of the country and poor visibility could affect drivers.
17 people were injured in Thame this morning as a Bus overturned on the M40, because of dangerous driving conditions.
Police are investigating and Sgt Mark Scully, of the Hampshire and Thames Valley joint operations unit, said the fog was dense at the time of the crash.
He told Sky News: “We are lucky at the moment we are not dealing with anything considered life-threatening.”
No arrests have been made, a TVP spokesman said.
An investigation into the 20-car crash on the A40 on Wednesday, in which one woman died and many other people were injured, is continuing and there have been no arrests, he said.
A weather warning has been issued urging drivers to be wary of fog and subzero temperatures across large areas of England.
A fog warning had been issued to drivers across swaths of England. The crash happened just 20 miles (32km) from a fatal pile-up on the A40 in Oxfordshire in similarly difficult driving conditions on Wednesday morning.
On Friday morning, Met meteorologist Emma Sillitoe said: "The main thing we have had is large, dense freezing fog patches.
"People driving around in the morning should take care on the roads."
Visibility could be as low as 100 metres and ice could develop on the roads, she added.
Transport for Buckinghamshire have issued the following statement on how drivers can be prepared for the upcoming conditions:
1. Don’t get caught out – be prepared:
Whether it’s raining heavily, blowing a gale, or below freezing outside you should check the weather forecast before making long journeys. It’s a good idea to keep an emergency kit in your car, should you encounter problems and become stranded; a fully charged mobile phone, some food (long life things like cereal bars), blankets, warm clothing, a torch, shovel, de-icer, a scraper, and a flask of hot tea or coffee are all sensible items to either keep in the car or grab before heading out on long journeys.
Your car itself should be prepared for winter too – the AA recommends taking certain measures to lessen your chances of a breakdown:
• Antifreeze – check coolant level regularly and, if required, top-up with a mixture of the correct type of antifreeze. Your garage should check concentration to ensure adequate cold temperature protection.
• Battery – the most common cause of winter breakdowns. A battery more than five years old may struggle in the cold - get it checked and replaced if necessary to avoid the inconvenience of an unplanned failure.
• Fuel – keep at least a quarter of a tank in case of unexpected delay.
• Lights – check and clean all lights regularly to make sure you can see and be seen clearly. Carry spare bulbs.
• Tyres – should have at least 3mm of tread for winter motoring. Consider winter tyres for improved safety. Check pressures at least every fortnight.
• Windscreen – reduce dazzle from the low sun by keeping the screen clean inside and out. Now is a good time to renew worn wiper blades.
• Screen wash – use a 50% mix of a good quality screen wash to reduce the chance of freezing in frosty weather.
• Locks and door seals – stop doors freezing shut with a thin coat of polish or Vaseline on rubber door seals. A squirt of water dispersant (WD-40) in locks will help stop them freezing.
Remember – no matter how well kitted out your car is for winter, there are other ways you can get stranded that aren’t due to a breakdown. A jack-knifed lorry, a fallen tree, or a snow drift could all cause you to become stuck in bumper-to-bumper traffic for hours at a time – that’s where the emergency kit comes in handy!
2. Driving to the conditions of the road
We advise all motorists to be responsible, diligent and safety-conscious when out on Buckinghamshire’s roads, particularly in adverse driving conditions. For instance, if you see a gritting alert on our website or Twitter, take it as a message that you need to adjust your driving to fit the conditions of the potentially icy road. There is plenty about ‘driving to the conditions’ in the Highway Code, which you can catch up on here, but we’ve summarised some of the main things you need to know.
Driving in ice or snow:
Keep a safe distance from other vehicles
Use fog lights appropriately
Only make necessary journeys and keep a ‘break down’ kit in your car (warm clothes etc)
Reduce your speed
If driving on snow or ice, accelerate and brake gently, and stick to higher gears.
Take bends slowly, and take into account the effect of ice on stopping distances when braking.
Be safe on the roads this winter, keep up-to-date via our website and Twitter, and please remember – just because it’s gritted, doesn’t mean a road is guaranteed to be ice-free. Grit is spread in order to reduce the risk of ice forming, not eliminate it completely.
Driving in fog
Use dipped headlights so that other drivers can see you.
If it is foggy (less than 100 m visibilities) then switch on your fog lights. Do not forget to turn them off when conditions improve.
Fog is often patchy so try not to speed up as visibility improves. You could suddenly find yourself back in thick fog further up the road.
3. Stay up to date with the gritting decision
Knowing whether or not we are gritting is important because it is an indication that you ought to adjust your driving, and not make unnecessary car journeys. The gritting decision is usually issued around lunchtime, sometimes later depending on clarity of temperature forecasts. It can be found on our website http://www.buckscc.gov.uk/transport/were-working-on-it/winter-maintenance/ or on Twitter https://twitter.com/twitgritter.
4. Things to remember about gritting:
Roads may still be icy – in the last week we have seen comments from a few residents asking why certain roads haven’t been treated at all – in actual fact, they have. Grit/salt is not a guarantee against ice. Treated roads may still be icy - no guarantee can be given that roads will always be completely clear of ice or snow. If we are responding to a late change in forecast, or if we have to wait for rain to clear before we salt, wet roads may freeze before they are salted. We cannot salt during wet weather as the salt would be washed away. In severe cold weather below -8ºC, even salt will not prevent ice from forming.