The warning is the key finding of the second Trafficmaster/ RAC Foundation UK Congestion Report, which reveals this Friday, October 19th, will be the worst day for travelling by car because of a peak in traffic congestion named 'Black Friday', by experts.
Traffic jams may be traditionally associated with Bank Holidays or Christmas, but a number of specific factors combine to make tonight's rush hour longer and more congested than any of Britain's regular public holidays.
These factors include darker (and possibly wetter) weather encouraging more drivers to use major roads, a high level of commuting and commercial traffic and a rise in accidents.
Philip Hale, spokesman for Trafficmaster, said: "It seems odd to think a Friday in October is busier than Christmas or Easter, but the 'Black Friday' phenomenon is very real and one all drivers should be prepared for."
According to the Trafficmaster UK Congestion Report, if the current trend continues, this year's congestion could be as much as 10%* worse than 2003.
Elsewhere in the report, the nation's worst congestion hotspot is revealed.
Up from second position six months ago, the Western sector of the M25 is officially the most congested stretch of road in Britain, replacing the M1 in Hertfordshire, where traffic has eased slightly thanks to a higher temporary speed limit.
The report also reveals the real traffic speed of the UK's motorways.
The average traffic flow speed of our motorways is a healthy 67.5 mph, although there are significant differences in their overall efficiency.
Scotland can boast both the most efficient motorway - the A74(M), with an overall real average speed of 69.9mph - and the least - the M8, at only 53.4mph.