Traffic modelling at the Port of Dover

Each year, 2.6 million lorries, 2 million cars and 12 million people move through the Port of Dover, representing 17% of the UK’s trade in goods. With freight traffic expected to increase by 40%, the Dover Eastern Docks Ferry Terminal’s half a kilometre-square site has to be managed as efficiently as possible.

Moving through the port requires passengers and vehicles to progress through a number of steps, beginning with French and then UK border controls; then comes Check-In, after which vehicles are marshalled in an Assembly Area prior to embarkation. At the entrance to the port, there are lanes which can hold 4km of traffic and, in extremely busy times, there are two protocols which can be enacted. First, freight vehicles can be held on the A20 road with traffic lights, to enable local and tourist traffic to pass by freely. Secondly, the M20 Motorway can be used as a lorry queuing area in what is known as ‘Operation Stack’; however, this is estimated to cost the UK up to £2 million per day in direct costs and lost productivity.

High traffic volumes can result from the ebb and flow of arrivals exceeding processing rates, meaning any potential bottlenecks needed to be identified and processes examined for optimisation. In addition, a range of future investment options need to be generated and evaluated.

The decision was taken to use discrete-event simulation to model road traffic flows, since the port consists of a series of process steps, each proceeded by orderly queues rather than a melee of interacting vehicles. The port is rich in data, with excellent historical data on ferry schedules, vehicle/passenger carryings and the arrival rates for different traffic types. The port has also invested in Blip Systems’ Blip-Track system which anonymously senses mobile phone and SATnav signals to monitor transit and dwell times of traffic on approach and through the port.

Modelling the port’s traffic flows provided a number of useful insights. The first was that the infrastructure can handle traffic well, and delays were generally because of technical issues rather than capacity limits, such as IT problems requiring slow manual check-in processes or staff shortages. Secondly, it showed the importance of the port’s Buffer Zone in providing flexibility within the system.

The next step was modelling future traffic volumes with three forecasts: expected, optimistic and pessimistic were created, based on varying assumptions and the use of sensitivity analysis to pinpoint future pinch-points. A key performance indicator was included, looking at the number of times a year the emergency traffic protocols had to be employed.

The model showed that the physical infrastructure of the port could suitably cope with future demand, albeit with greater staffing levels to handle traffic increases.  Modelling also identified a costed, sequenced set of investments that optimally addressed traffic growth, together with critical traffic volume thresholds that should trigger investments in the future.

The model had several positive impacts, both tangible and intangible. These were saving money and resources, and facilitating dialogue with government agencies respectively. There were further benefits in the form of the development of a few simple principles that can be applied:

• The value of flexibility: given the intrinsic variability in traffic flows, no single fixed configuration of the port’s hard infrastructure could be optimal all of the time. Any investments which increase flexibility are to be welcomed.
• Key questions help evaluate future plans: Does it increase capacity? Does it improve fluidity? Does it enhance flexibility? Does it increase resilience?
• Recognise the difference between ‘anatomy’ of the port (infrastructure) and the ‘physiology’ (how it works), and how to adapt performance by changing incentives rather than infrastructure changes
• Understanding the importance of modelling to support planning: forecasting and analytics serves an important role in supporting real-time, evidence-based decision-making.

Full article available in Impact Magazine, Spring 2018: ‘Traffic Modelling at the Port of Dover pp7-11