Drivers in parts of England are being urged to plan ahead and consider if their journey is essential due to snowfall.
National Highways, which manages motorways and major A roads, issued a severe weather alert for the South East and South West between midday on Wednesday and 3am on Thursday, and for the West Midlands and East between 3pm on Wednesday and midnight.
The Government-owned company warned that driving conditions will be “extremely difficult, especially for larger vehicles and those not equipped with four-wheel drive”.
Motorists in areas covered by the alert are urged to “consider if their journey is essential”.
National Highways said lorry drivers are “asked to consider avoiding parts of the road network with steeper than normal inclines”, such as the M40 from Junctions 4 to 5, and the A49 in Shropshire.
This is because of the risk of their vehicles becoming jack-knifed or stranded in wintry weather.
National Highways executive director of operations Duncan Smith said: “We are well prepared and our gritters have been out in full force since Friday, and will continue to treat the roads.
“We are asking drivers to plan ahead, check the forecast and allow more time for their journeys.”
The company warned there could be a “more significant second wave” of snow from Wednesday afternoon.
It added that snowfall “will be prolonged and occasionally heavy, particularly during the evening rush”.
Drivers were warned to expect “possible travel delays on roads with some stranded vehicles and passengers”, while “some rural communities could become temporarily cut off”.
Councils are also gritting local roads and pavements in a bid to ensure people can keep moving.
David Renard, transport spokesman for the Local Government Association, said: “As temperatures plummet once again, councils are ready to work around the clock to grit roads and pavements to make sure that people are kept safe and local communities can get out and about.
“Councils have stockpiled 1.4 million tonnes of salt and are using new and innovative technologies where they can to ensure those areas that are most treacherous are kept clear and safe for use.”
RAC spokesman Rod Dennis said: “While we saw an increase in breakdowns in a zone that stretched from London west along the M4 corridor and into Wales earlier this morning, based on our breakdown volumes it seems drivers in many snow-affected areas are choosing to work from home today and not get in their cars in the first place.”
Rail passengers are being warned to expect weather-related disruption.
Network Rail Kent and Sussex said: “Snow that fell overnight is impacting a few services this morning. Please check before you travel.
“More snow is forecast this afternoon with disruption to services expected from 5pm onwards. Please consider travelling home earlier than usual.”
Govia Thameslink Railway said: “Until the morning of Thursday March 9, snow showers are expected at times, although not all areas of the network will be equally affected.
“Ice will cause an additional hazard, especially overnight.
“Staff are working hard to minimise any disruption, but there could be some changes to trains.”
It added: “Staff have re-allocated some newer trains to Southern services along the south coast.
“This will ensure that older trains are withdrawn for the affected period, as they are less suitable for poor weather.”
This means some services will have fewer carriages than normal.
