Slow moving lorries on hills and crashes are causing chaos on roads across Beds, Herts and Bucks.
Black ice and snow is leading to poor conditions, with heavy volumes of slow moving traffic causing congestion.
An earlier accident in Hertfordshire blocked the westbound A505 at Ashwell and tailbacks took a time to clear.
Traffic is also very slow on the A507 in Bedfordshire and on the A6 between Biggleswade and Luton, with an accident near Silsoe causing long delays.
Accidents around Leighton Buzzard and Aylesbury are also causing traffic hold-ups.
Luton Airport was closed for an hour earlier so that snow could be cleared from the runway.
Many trains are running to amended schedules and services between Watford Junction and Harrow are suspended because of ice on the rails.
Police are asking drivers to take care and also to consider if their journey is really necessary.
More severe snowfall is expected in the area later.