Warning to drivers over snowfall in Essex
Essex Police are urging people only to drive if necessary after heavy snowfall overnight.
Major routes are passable, with police urging extreme caution. Part of the A12 is closed after a lorry hit the central barrier and spilled diesel.
The East of England Ambulance Service said it had to take four people in Colchester, Southend and Harlow to hospital due to exposure to the cold.
The two women and two men were walking in the street in the early hours.
Weatherquest, based at the University of East Anglia, said temperatures could drop to -1C with a risk of ice overnight.
There is a chance of some sleet or rain on Monday and Tuesday.
Neighbours help ambulance
The ambulance service said it was "extremely busy" in the early hours of Sunday, with its crews dealing with difficult driving conditions.
The number of calls to the service between 23:00 GMT on Saturday and 09:00 GMT on Sunday were up by about 25% on last week, it said.
It asked for patience and for people to only call 999 in a real emergency.
Response times can be sped up if patients' relatives, friends or neighbours ensure access is clear to driveways and paths, it added.
Medical technician Barry Withers said he and student paramedic Keith Colam called on help from neighbours when Sarah Alder went into labour at home in Basildon.
The pair arrived in a rapid response car at 06:30 BST, but needed a midwife - who could not get to Ascot Grove in the snow.
An ambulance was called and got stuck, but Wayne Bond of Vine Close and Daniel Rice from Warren Drive dug away the snow to allow the ambulance and response car to leave the cul-de-sac, Mr Wither said.
Ms Alder, partner Stephen Watson and baby Megan could then be taken to hospital.
A lorry had hit the central barrier at an underpass on the A12 earlier, spilling diesel and forcing the closure of the road at junction 12 for Shenfield.
Essex Police said the Colchester-bound carriageway will have to be shut for some time on Sunday for repair work to the central reservation.
Motorists are advised to listen to local radio for updates when the road is re-opened.