Motorists have been urged to take extra care as the UK braces itself for snow and icy conditions.
Forecasters have warned more snow is expected after blizzards disrupted travel and closed schools in Scotland yesterday.
The Met Office has issued an amber "be prepared" alert across central and southern Scotland today, with Wales, Northern Ireland and much of England also on alert.
Gritters were out in force last night and commuters have been told to expect some delays and cancellations of services.
Network Rail has suspended four train routes and the AA said its crews were ready for a busy 48 hours.
Darron Burness from the AA's severe weather team said: "It's a case of 'expect the unexpected' and drive accordingly.
"Untreated roads could be slippery, so keep your distance and watch your speed, as things can go wrong very quickly on snow and ice.
"If conditions are bad, even short journeys can take significantly longer, so allow extra time, as some delays are to be expected. Also make sure your car's windows and lights are clear of snow and frost before heading off."
The wintry blast took effect in Scotland yesterday morning, forcing the closure of more than 30 schools in the Highlands and creating difficult driving conditions.
In Dundee, a six-vehicle crash saw a car slide off the road and crash through railings into the wall of a property and a lorry jackknifed near Carrbridge on the A9.
The Met Office said yesterday: "There is a risk of two spells of persistent snow. The first of these is likely to cross the amber area on Tuesday evening, with another one affecting the area on Wednesday morning - both of which could produce disruptive snowfall during busy travel periods.
"Meanwhile, snow is likely to continue to accumulate throughout this period on high ground.
"The public should be prepared for the risk of disruption and difficult driving conditions."
The amber warning, in place until 10am, follows last week's fierce storms which left 120,000 properties without power in Scotland.
The homes have since been reconnected but BT is continuing to fix phone lines in the Highlands and Islands.
Repair efforts have been hampered by fallen trees, ferry cancellations and traffic restrictions.
Road operator Bear Scotland said its teams were working around the clock to keep routes clear, while Police Scotland said drivers should ask whether their journey is really necessary before getting behind the wheel.
Chief Inspector Louise Blakelock said: "If you do decide to travel, ensure your vehicle is well prepared before setting off, make sure your windscreens are completely free of snow and ice, and your lights are working and clean."
Network Rail said a limited number of train services would be suspended from noon today, when the worst of the winds are expected to strike.
No trains will run on the Dumbarton Central to Helensburgh Central and Glasgow to Oban lines until 6pm tomorrow.
The Kyle to Dingwall and Kilwinning to Ardrossan line will also be suspended.
David Dickson, route managing director for Scotland, said: "Safety has to be our first consideration during severe weather. Where conditions are predicted to be most severe, we have agreed to withdraw a limited number of services until the worst of the storms have passed.
"During periods of snow and extreme cold we use a number of measures to keep the network open including insulated points heaters to prevent freezing, snow ploughs to remove drifts and our snow train which uses hot air blowers and steam to thaw frozen parts of the network.
"Our teams are out on the network and will be working around the clock to keep the tracks clear."
A yellow "be aware" warning for snow and ice remains in place across Wales, Northern Ireland and much of England, with sleet and snow showers possible overnight.
The Met Office said: "This is most likely to occur in the west of the yellow area, with the high ground of Wales, the moors of south-west England, the Mendips and Cotswolds at greatest risk of snow accumulations.
"A lower risk exists across south-east England early on Wednesday morning. Icy stretches will also form on untreated surfaces."
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