Fresh snowfall and a drop in temperatures overnight have prompted Sussex Police to issue a fresh warning to motorists.
A senior traffic officer said drivers should not set out on journeys “unless they are absolutely necessary”.
The snowfall yesterday has frozen hard, the force said, and “road conditions are extremely hazardous, even on some of the county’s main A routes”.
Chief Inspector Di Roskilly, of the Sussex Police Road Policing Unit, said: “If you do have to set out, plan your route and leave much more time for your journey.
“Drive slowly to take account of the treacherous conditions and leave a good distance between your car and any vehicles in front of you.
“Make sure that your car has enough fuel for what may turn into an extended journey – you may need to keep yourself warm – and essentially, ensure that your windscreen wipers and wash bottle are free of ice and working effectively.
“Be especially careful of pedestrians walking in the road as pavements may be hazardous.
“If you are walking or cycling, wear something highly visible so that you can be seen and be aware that vehicles may not be able to stop quickly.”
Neil Hopkins, the communications manager for the Sussex Safer Roads Partnership (SSRP), said: “We advise that motorists travel with blankets, food and a flask of hot drink in case of a breakdown or emergency.
“Ensure you have a mobile phone with you and it is fully charged, particularly if you are making a longer journey.”
Dozens of train services are again being cancelled. Updates on Southern services can be found here.
A limited bus service is running. Updates from Brigton and Hove Buses can be found here.
The company said: “We have fitted snow chains to some coaches and we are using these on service 7 so we can provide a service to parts of the city that normal buses cannot reach.
“As soon as the 7 route becomes passable with normal buses we will divert the snow-chained coaches to more outlying areas.”