Drivers are being warned to expect delays today - with an 'amber' traffic alert in place due to the bank holiday getaway.
Roads in Cornwall, Devon and Somerset are expected to be particular hotspots with traffic levels due to peak today (Friday 26 August).
Scroll down for the latest updates...
Breakdown service provider RAC estimates that nationally 12.5 million leisure journeys will be made by car between Friday and Monday night.
It is urging motorists to be prepared for long delays and set off early in the morning to avoid the worst of the queues. Friday is expected to be the most popular day for trips.
The RAC is also advising drivers check their cars before setting off on their journeys.
The RAC's Rod Dennis added: "If you’re aware of any existing problems with your car, get these checked out by an approved garage before setting out – a long drive is not the time to put your car to the test.”
The latest South West traffic updates
M5 southbound: Holiday traffic is causing congestion between J17 (Cribbs Causeway) and J20 (Clevedon). Travel time is 50 minutes.
M5 northbound: There are long delays and stop-start traffic due to holiday queues between J25 for Taunton and J17 for Cribbs Causeway. Travel time is one hour and 10 minutes.
M4 westbound: There is very slow traffic on M4 westbound from J18 (Bath/Tormarton) to J21 for the M48. Travel time is 30 minutes.
M4 eastbound: One lane closed and very slow traffic due to broken down vehicle on M4 Eastbound from J20 (Almondsbury Interchange) to J19 (Bristol).
A303: The A303 is partially blocked in both directions with slow traffic due to an accident near A30. The section past Stonehenge has been highlighted by Highways England as a particular hotspot for congestion.
A30: Reports of queueing traffic due to an accident on A30 at Henver Lane which is not helped by extra holiday traffic. Congestion is building on the A30 eastbound between the A382 and the junction with the A377. National Highways says there are delays of around 15 minutes.
M32: There is congestion on the M32 southbound at junction three. According to Inrix, There are delays of around 10 minutes.
More updates to follow.