Both Severn bridges are shut after ice fell onto cars and smashed windscreens as a fifth day of weather chaos blights Britain. As heavy snow brings parts of the UK to a standstill, the Severn Crossings, the two main roads between England and South Wales, have been shut for safety reasons. Jim Clune, general manager of Severn River Crossing Plc, said: "The situation is that bridge closures have been requested because there were reports of sheets of ice falling from overhead sign gantries and smashing car windscreens. "It's very much a safety hazard and of course these gantries span all carriageways on the motorways. We have had reports of sheets of ice up to one metre square. Five vehicles have reported windscreens smashed from falling sheets of ice." Meanwhile, around 200 people were rescued from their cars overnight in an emergency operation involving police, Army and civilian teams after becoming stranded on the A38 and A380 in blizzard conditions south of Exeter in Devon. Some were forced to spend the night in their vehicles as temperatures plummeted outside while others abandoned their cars and sought refuge in nearby garages and hotels. Motorist Lucy Johnson: "It was horrific. I've never driven in anything like it before in my life and hope to never drive in anything like it again. Cars were skidding off the road. It was coming down so heavily you could barely see." Barry Johnson, clerk of the course at Exeter Racecourse, trudged three miles uphill through the snow from his home in Kennford to open it as an emergency shelter for around 50 people who were served hot drinks and pasties through the night. He said: "Everyone's been quite jovial. It was such a freak event it took us by surprise. I have heard nobody moan at all but they all want to go home now." A pregnant woman, who went into labour and was rushed to a small community hospital, praised NHS staff after giving birth to twin girls. Andrea Dunn, of North Tawton, Devon, was due to give birth at the Royal Devon and Exeter Hospital, but had to be diverted to Okehampton Community Hospital. She gave birth in the early hours of Friday morning before being flown by Sea King helicopter with her babies to the North Devon District Hospital to have health checks. Ms Dunn said she and husband were extremely grateful for the efforts of the emergency services. She said: "I just want to say thank you to the NHS and the emergency services for all they have done to help and for making sure that my babies arrived safely." With temperatures dropping as low as minus 8C (17.6F), councils across the country are also perilously close to running out of salt and grit with some forced to ration its use. In the West, more than 800 schools are closed as staff and pupils struggle to get through the snow after around 4in-5in (10cm-13cm) fell in an hour. All schools in Bath and North East Somerset are closed, along with around 150 in Somerset. More than 300 in Wiltshire, including Swindon, have shut and over 200 across Gloucestershire. Bus services are suspended across Bristol, South Gloucestershire, Bath and North Somerset and the M5 motorway in Somerset is down to one lane in both directions as traffic slowed to 30mph. First Great Western train services between Bristol Temple Meads and Severn Beach are suspended, with no replacement transport available, because of poor rail conditions. And all flights at Luton airport are suspended with dozens of flights cancelled. Bristol International Airport has reopened to run a limited number of flights but long delays are expected.