As the end of the Brexit transition period looms, many might have hoped the new year will mean the end of Operation Stack, the dreaded traffic management system which has been deployed in the county for two decades to deal with congestion heading to the Port of Dover.

Involving the closure of the M20, Operation Stack allows HGVs to be “stacked” on the motorway with other traffic diverted on to the A20.

It was triggered on Sunday night, after the French government banned all freight and passenger traffic from entering their country.

This morning, Operation Stack was replaced by Operation Brock, with a contraflow system in place between Ashford and Maidstone on the M20, as talks between the French and UK government continue and the ports remains closed.

The motorway was closed at 8pm yesterday to allow for a moveable barrier which creates the contraflow to be put in place.

When asked why Operation Stack was put in place on Sunday night, rather than Op Brock, Kent Police said: "Operation Brock, which is managed by Highways England, is designed for long-term travel disruption and requires overnight closures to be put in place on the M20.

"The decision of the French authorities to enforce a travel ban for traffic arriving from the United Kingdom created an urgent and immediate need for a traffic management system, that deals with any potential disruption, to be put in place.

"The decision to implement Operation Stack was taken following consultation with partners within the Kent Resilience Forum and is an emergency measure. It is only used when the volume, or predicted volume, of freight on Kent’s roads poses a serious risk to public safety.

"Kent Police regularly met with partners throughout the day and a section of the M20 was closed overnight to allow Operation Brock to be put in place."

As statement suggests, Operations Stack and Brock have different roles, but what will be their purpose next year and why have we still not seen the back of Operation Stack?

Both systems could be deployed as part of Operation Fennel, the overarching response to disruption on the roads caused by Brexit, which includes numerous strategies and has been devised by emergency planners and the government.

According to the Kent Resilience Forum (KRF), which is working with the government to prepare for problems on the roads in January as new border checks and custom declarations are bought in, Operational Fennel "is designed to cope with 7,000 HGVs....the maximum queue length of HGVs expected in Kent."

So where does Operation Stack fit in with this?

It has been the default contingency plan to address congestion and delays principally on the M20 and pre-dates Brexit by two decades.

Its origins lie in an attempt to provide a solution to delays at Kent’s cross channel ports caused by bad weather or striking French workers. Ironically, it was first deployed in February 1988, because of a strike called by the National Union of Seamen in Folkestone Docks.

But, Operation Stack will still have a role, albeit a smaller one, to play in the future.

KRF says that Operation Brock has been "developed as a preferred option to Operation Stack." The aim is for Operation Stack to be "implemented as a last resort".

Outlining the plans, KRF says: "It is accepted that Kent Police and partners may have a scenario where Operation Stack is necessary. "Operation Stack could therefore be introduced at any stage of the Operation Fennel Plan as an emergency contingency measure, depending on the threat and risk presented."

"Compromised capacity can occur spontaneously", KRF says, and reasons include industrial dispute, weather conditions, a major incident, or other events affecting the capacity of either the Port of Dover or the Channel Tunnel.

Whereas Op Stack sees the closure of the M20, the aim of Op Brock is designed to keep the motorway flowing by operating a contraflow system between junctions 8 and 9 on the London-bound carriageway.

The contraflow is for all traffic other than HGVs heading to the ports. The coast bound carriageway is utilised for port bound freight.

A moveable barrier will create the contraflow and will keep the M20 open in both directions. The scheme is managed by Highways England and has the capacity to hold 2,000 HGVs.

The coast-bound carriageway can be used in two ways. The first is port-bound freight flowing freely and the other is freight being held in two lanes, using traffic signals and being released to Eurotunnel or Port of Dover, from one lane on the A20, as capacity becomes available.

Op Brock was due to be implemented next week ready for the end of the Brexit transition period but the closure of the port forced highways bosses to bring it in last night.

A huge post-Brexit lorry park is also being built for use in the new year, next to Junction 10a on the M20 in Ashford.

The 66-acre site is set to comprise two areas - one will be a holding area for up to 1,700 trucks, while the other will be a HMRC customs check facility.

Keep up-to-date with developments on transport and stories that will impact how you travel

Read more: All the latest news from Kent

Read more: All the latest news from Dover