Snow and icy conditions have caused a series of road accidents across Sussex leaving thousands of people trapped in travel chaos.

Despite gritters being sent out in force yesterday, police and emergency services have been inundated with calls of cars sliding off roads and vehicle pile-ups.

Motorists were left stranded as their cars skidded across ice and lorries jack-knifed as they tried to cope with the region's biggest snowfall since 1997.

Sussex Police said the force had 56 weather-related calls in just 15 hours and were expecting the figure to double last night.

Sergeant Marc Clothier, of Brighton and Hove Road Department of Sussex Police, said: "I can't recall when we have had such an extreme period of cold weather.

"It is fair to say that most of my unit have been taken up with incidents or collisions that are weather-related due to bad road conditions. The majority of the problems are because visibility isn't great and the roads are slippery.

"I imagine it will be getting colder again so I am expecting more snow. You don't often get prolonged periods of snow and ice, so motorists are just not used to the conditions."

Weather forecasts predict widespread problems on roads for another couple of days which hauliers say could delay deliveries and cause problems for supermarkets, retailers, factories, offices, schools and hospitals.

School children were the only ones to benefit as they enjoyed a rare day off as 120 schools across Sussex were forced to shut down because teachers could not get to work.

The bad weather took Sussex by surprise and police and emergency services have been working around the clock to deal with incidents.

A six-car pile-up caused tail-backs at Southwick Tunnel on the A27 near Shoreham yesterday and a car skidded and flipped onto its roof due to the frosty conditions on the A26 near Uckfield.

Other accidents include a two-car collision on Dyke Road towards Devils Dyke, during which one car skidded off the road.

Lorries were backed-up on Winchelsea Hill on the A259 after one got stuck and blocked the road.

One car slid off the road at Monks Walk, Winchelsea, while another crashed into a lampost on the A259 towards Hastings.

In Strand Hill, Winchelsea, residents put their wellies on and helped out the gritters by throwing salt onto the roads by hand.

Brighton and Hove City Council sent out its seven road gritters. Five were on their normal routes gritting hills on the outskirts of town and two extra ones were made available for emergencies.

East Sussex County Council sent out its entire 15-strong fleet of gritters, and several vehicles were later fitted with snowploughs.

A MET office spokesman said: "Sussex is definitely the worst affected area of the country, but Kent and Essex are also badly affected.

"A lot of places could see between two and 5cm of snow, particularly at higher ground level. The Downs is likely to see up to 10cm of snow."

He said the conditions were expected to clear up by mid-morning today as the depression moves across the South East and over to France. But he warned that temperatures as low as minus degrees last night could mean another snowfall.

Rail passengers also had long delays after the bad weather, coupled with signal and train failures, threw the morning rush hour into chaos.

Wintry conditions in Kent resulted in cancellations and long delays to South Eastern Trains services in the Tunbridge Wells area. Travellers on Southern and Thameslink services also had troubled journeys after signal failures between Brighton and Haywards Heath.

A Sussex Police spokeswoman said the most badly-hit areas include Crowborough, which has thick ice, Hangleton in Hove and the village of Exceat near the A259.

Alfriston, near Polegate in East Sussex, was also hit by heavy snowfall and Winchelsea, towards Rye in East Sussex, was completely cut off.

Weather expert Ken Woodhams, of Hove, said: "This is the first real snow we have had since December 1997. It is not unusual for this to happen, although we usually only get a light dusting.

"It's about an inch at the moment but it keeps melting and won't lay. It's what I call wet snow."

Three quarters of pupils at St Peter's Primary School, East Grinstead Road, North Chailey, were left without teachers because of the severe weather yesterday and the school was forced to close.

Three of the four class teachers for the school's 95 pupils were stuck in snow drifts across the county.

Secretary Sarah Main said: "It was a bit hectic. One teacher was snowed in Crowborough and the other two were in Eastbourne. It took the headteacher an hour-and-a-half to get in from Brighton.

"We tried to get hold of the radio station, put signs up outside and cancelled the school bus."

In Brighton and Hove, Falmer High School, Woodingdean Primary School and Downs View Special School were closed yesterday and it is expected that Dorothy Stringer, Patcham High and Carlton Hill Primary School will be closed today.

No schools have been closed so far in West Sussex.

An East Sussex County Council spokesman said: "We have just over 200 schools in the county and about 120 of them were closed yesterday. With the weather forecasts we are anticipating more closures."

The Freight Transport Association, which represents companies operating over 200,000 goods vehicles, has warned that ploughs, gritters and salters need to keep roads open so deliveries can get through.

A Sussex Police spokeswoman said: "We would ask motorists to take care, slow down, use your lights, plan your journey and listen to the local radio for the latest updates.."

For latest information on school closures visit www.southernfm.com. For latest weather updates visit www.met-office.gov.uk.