Police have warned that disruptions are possible during Monday's fuel protest, when slow-moving vehicles could block the Prince of Wales Bridge.
The bridge connecting England and Wales, and the M5 running from Somerset to Bristol are two of the most important routes that could be affected.
Avon and Somerset Police advised that the M4 between Almondsbury and the M32 could also be affected.
According to Paul Wigginton, journey times are likely to be longer than usual.
He said, "Working alongside Gwent Police we are engaging with all organisers of these demonstrations."
"People have the right to peaceful protest. Liaison teams from Somerset, Avon, and Gwent have been trying to understand campaigners plans to maintain public safety and reduce disruptions to other people.
"But, drivers should expect longer journey times, especially on main roads and motorways, during peak times.
We advise motorists to consider alternative travel plans and be prepared for any delays.
Protests have been planned to protest the recent rise in petrol and diesel prices.
According to the RAC, the average cost of filling a family vehicle is more than PS100.
Because crude oil has increased in price, fuel prices have risen sharply. This is what makes petrol and diesel.
US dollars are used to pay for the oil that is used in making petrol. Fuel is more expensive because the pound is currently weaker against the dollar.
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