Fuel price protesters will cause disruption on major roads in south-west England on Friday.
Avon and Somerset Police warned motorists that “slow-moving roadblocks” are planned on parts of the M4, M5, M32 and A38.
An image posted on the Facebook group Fuel Price Stand Against Tax suggests demonstrations will be held “nationwide”, including in Birmingham, Cardiff, Liverpool, London and Manchester.
This could cause disruption to the millions of families embarking on getaways at the start of summer holidays for many schools in England and Wales.
Superintendent Tony Blatchford of Avon and Somerset Police said: “Our protest liaison team has been engaging with the organiser so we can inform the public of the likely disruption and help to minimise it.
“Nevertheless, drivers can expect journey times will likely be longer than normal, especially on motorways, which often tend to be at their busiest at this time of year.
“We advise motorists to consider any alternative travel plans available and ensure they are suitably prepared in case they are delayed.”
Fuel price protests on July 4 led to 12 people being arrested on the M4.
The first stage of Friday’s action in the South West will see vehicles travel north on the M5 between Bridgwater and the Almondsbury Interchange from around 8.45am, then east along the M4 and to Junction 1 of the M32.
The convoy is expected to leave the motorway and stop “for a period of time” before completing the same route in reverse, arriving back in Bridgwater “in the early afternoon”, police said.
A second group of protesters is planning to drive slowly to the Shell petrol station in Bristol Road, Bridgwater.
“They are expected to block the forecourt during the morning,” according to police.
Figures from data company Experian show the average price of a litre of petrol on Wednesday was 187.5p, while diesel was 196.1p.