Operation Brock

Everything We Know About Operation Brock for Dover & Folkestone

The Operation Brock contraflow system is designed to keep traffic on the M20 and other roads in Kent moving when there is disruption to travel across the English Channel.

When there’s any sort of disruption in the channel, HGV traffic on the M20 heading for the Port of Dover or the Eurotunnel has nowhere to go.

That’s why there’s now a contraflow system in place, that we call ‘Brock’, which can be set up overnight. It separates traffic into different lanes across both carriageways and keeps the M20 and other local roads open and moving.

It means, once the contraflow is in, if you’re on the M20 but not going to the port or LeShuttle (Eurotunnel), you can continue your journey as normal. At the same time, it helps control how port-bound HGVs make their way to the Port of Dover or the LeShuttle (Eurotunnel).


National Highways use these alerts to tell you the status of Operation Brock:

  • RED - M20 is closed
  • AMBER - M20 is open but contraflow in use
  • GREEN- M20 is running as normal (no contraflow)

How often is the contraflow in use?

Most of the time the contraflow won’t be in use – that means the M20 is running completely as normal.

Why do we close the M20?

To safely install the contraflow we must close the motorway overnight. During these closures clearly signed local diversions will be in place. When we reopen the M20 the contraflow will be in place and in use.

What to do if the contraflow is in use

If you see that the contraflow is ‘in use’ you can still use the M20, but you should allow more time for your journey. Because it’s a contraflow and the road layout is different, a speed limit of 50 mph will be in place. This also means the motorway continues to run in both directions.

If you’re not going to the ports but travelling within Kent, all you need do is get into the correct lane and drive through the temporary lane layout within the speed limit.

If you’re travelling to the ports or the Eurotunnel when the contraflow is in it means there’s disruption across the channel. Please check with your ferry or train operator to see if you should travel. If you go ahead with your journey, once you get to junction 8 on the M20 you’ll need to join the correct lane where you’ll be held as we’ll be managing the flow of traffic into the ports.

If you’re coming into the UK and using the M20, between junctions 9 and 8 you’ll use the two-way contraflow system on the London-bound carriageway. A 50mph speed limit will be in place. Signs will guide you into the contraflow at junction 9 and out at junction 8.

For more information, visit the National Highways Operation Brock travel updates page.

28 March 2024

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