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PA
Plans to tackle post-Brexit traffic queues by holding lorries in a disused Kent airport are being put to the test.
More than 100 HGVs will travel the 20-mile route from Manston Airport, near Ramsgate, to the Port of Dover from 08:00 GMT.
Hauliers fear a no-deal Brexit will create additional border checks, leading to queues of up to 29 miles.
The government said it had to "prepare for all eventualities... including a possible no deal".
The trial, between 08:00 and 11:00 GMT will test how the A256 copes with increased lorry traffic.
Operation Brock is intended to maintain traffic flow on the M20 and prevent the kind of disruption experienced in 2015, when parts of the motorway were closed to cars for several days.
The trial has been organised alongside the Road Haulage Association (RHA) and the Freight Transport Association.
Ramsgate 'not ready'
Disruption is expected as the trial coincides with the day many people return to work and school for the first time since Christmas.
Duncan Buchanan of the RHA said it should have been done nine months ago.
"These sort of practical, pragmatic tests need to be done - it just shouldn't be done as late as this," he said.
Mr Buchanan said import and export businesses on both sides of Channel had "no idea how they are going to deal with the customs process" under a no-deal Brexit.
There was a warning on Sunday the Port of Ramsgate could not be ready for a no-deal Brexit.
A freight firm has been given a contract to run a freight service between Ramsgate and Ostend in the event there is no deal.
Prime Minster Theresa May is attempting to persuade MPs to support her draft deal.
They are expected to vote on it on 14 or 15 January.