Heavy snow has fallen across Essex
Main roads in Essex are being prioritised for gritting because salt stocks are running low, the county council has said.
Police have warned drivers of "treacherous" conditions and urged people to only make necessary journeys.
More than 470 schools in Essex have closed because of the severe weather conditions hitting the county.
The council said it will reduce gritting over the weekend to ensure roads get salt during the working week.
Untreated roads warning
Roads have been gritted for 23 consecutive days and the council is facing "unprecedented conditions", a spokesman said.
Its 65 winter gritters will be operating on a reduced precautionary network on Friday and Saturday evening.
This will include all A roads, some B roads and other roads serving larger towns and villages, as well as access to major hospitals, fire and ambulance stations.
It will aim to return to its normal gritting programme by Sunday evening.
Norman Hume, cabinet member for highways and transportation, said: "Our gritters and crews have been out night and day for three weeks treating 1,800 miles of Essex's primary network plus hundreds more miles of high footfall areas.
"I would like to ask the public to take special care on untreated roads and continue to travel with extreme caution at this time."
The East of England Ambulance Service's Chelmsford control room has had a huge increase in calls in the past few days.
The service has hired extra four wheel drive vehicles to get to emergency callouts during the icy weather.
Police said the highest number of calls they received was about "anti-social snowballing".
The Met Office said sub-zero temperatures overnight would freeze much of the snow, with temperatures falling as low as -8C (17.6F).
It said the cold snap was likely to last until the middle of January.